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573 lines
21 KiB
Text
573 lines
21 KiB
Text
ALTER DATABASE test CHARACTER SET latin1 COLLATE latin1_swedish_ci;
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set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
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set long_query_time=0.1;
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TEST GROUP 1:
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Typical cases of in-to-exists and materialization subquery strategies
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=====================================================================
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drop database if exists world;
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set names utf8;
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create database world character set latin1;
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use world;
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CREATE TABLE Country (
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Code char(3) NOT NULL default '',
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Name char(52) NOT NULL default '',
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SurfaceArea float(10,2) NOT NULL default '0.00',
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Population int(11) NOT NULL default '0',
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Capital int(11) default NULL,
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PRIMARY KEY (Code),
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UNIQUE INDEX (Name)
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);
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CREATE TABLE City (
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ID int(11) NOT NULL auto_increment,
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Name char(35) NOT NULL default '',
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Country char(3) NOT NULL default '',
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Population int(11) NOT NULL default '0',
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PRIMARY KEY (ID),
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INDEX (Population),
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INDEX (Country)
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);
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CREATE TABLE CountryLanguage (
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Country char(3) NOT NULL default '',
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Language char(30) NOT NULL default '',
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Percentage float(3,1) NOT NULL default '0.0',
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PRIMARY KEY (Country, Language),
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INDEX (Percentage)
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);
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Make the schema and data more diverse by adding more indexes, nullable
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columns, and NULL data.
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create index SurfaceArea on Country(SurfaceArea);
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create index Language on CountryLanguage(Language);
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create index CityName on City(Name);
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alter table City change population population int(11) null default 0;
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select max(id) from City into @max_city_id;
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insert into City values (@max_city_id + 1,'Kilifarevo','BGR',NULL);
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SELECT COUNT(*) FROM Country;
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COUNT(*)
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239
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SELECT COUNT(*) FROM City;
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COUNT(*)
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4080
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SELECT COUNT(*) FROM CountryLanguage;
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COUNT(*)
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984
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set @@optimizer_switch = 'in_to_exists=on,semijoin=on,materialization=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on';
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1. Subquery in a disjunctive WHERE clause of the outer query.
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Q1.1m:
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MATERIALIZATION: there are too many rows in the outer query
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to be looked up in the inner table.
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EXPLAIN
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SELECT count(*) FROM Country
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WHERE (Code IN (select Country from City where City.Population > 100000) OR
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Name LIKE 'L%') AND
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surfacearea > 100000;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country ALL Name,SurfaceArea NULL NULL NULL 239 Using where
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2 MATERIALIZED City ALL Population,Country NULL NULL NULL 4079 Using where
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SELECT count(*) FROM Country
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WHERE (Code IN (select Country from City where City.Population > 100000) OR
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Name LIKE 'L%') AND
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surfacearea > 100000;
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count(*)
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107
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Q1.1e:
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IN-EXISTS: the materialization cost is the same as above, but
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there are much fewer outer rows to be looked up, thus the
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materialization cost is too high to compensate for fast lookups.
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EXPLAIN
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SELECT Name FROM Country
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WHERE (Code IN (select Country from City where City.Population > 100000) OR
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Name LIKE 'L%') AND
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surfacearea > 10*1000000;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country range Name,SurfaceArea SurfaceArea 4 NULL 5 Using index condition; Using where; Rowid-ordered scan
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2 DEPENDENT SUBQUERY City index_subquery Population,Country Country 3 func 17 Using where
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SELECT Name FROM Country
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WHERE (Code IN (select Country from City where City.Population > 100000) OR
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Name LIKE 'L%') AND
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surfacearea > 10*1000000;
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Name
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Russian Federation
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Q1.2m:
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MATERIALIZATION: the IN predicate is pushed (attached) to the last table
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in the join order (Country, City), therefore there are too many row
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combinations to filter by re-executing the subquery for each combination.
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EXPLAIN
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SELECT *
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FROM Country, City
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WHERE City.Country = Country.Code AND
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Country.SurfaceArea < 3000 AND Country.SurfaceArea > 10 AND
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(City.Name IN
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(select Language from CountryLanguage where Percentage > 50) OR
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City.name LIKE '%Island%');
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country ALL PRIMARY,SurfaceArea NULL NULL NULL 239 Using where
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1 PRIMARY City ref Country Country 3 world.Country.Code 17 Using where
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2 MATERIALIZED CountryLanguage ALL Percentage,Language NULL NULL NULL 984 Using where
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EXPLAIN
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SELECT *
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FROM Country, City
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WHERE City.Country = Country.Code AND
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Country.SurfaceArea < 500 AND Country.SurfaceArea > 10 AND
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(City.Name IN
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(select Language from CountryLanguage where Percentage > 50) OR
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City.name LIKE '%Island%');
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country range PRIMARY,SurfaceArea SurfaceArea 4 NULL 32 Using index condition; Rowid-ordered scan
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1 PRIMARY City ref Country Country 3 world.Country.Code 17 Using where
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2 MATERIALIZED CountryLanguage ALL Percentage,Language NULL NULL NULL 984 Using where
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SELECT *
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FROM Country, City
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WHERE City.Country = Country.Code AND
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Country.SurfaceArea < 500 AND Country.SurfaceArea > 10 AND
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(City.Name IN
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(select Language from CountryLanguage where Percentage > 50) OR
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City.name LIKE '%Island%');
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Code Name SurfaceArea Population Capital ID Name Country population
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CCK Cocos (Keeling) Islands 14.00 600 2317 2317 West Island CCK 167
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Q1.2e:
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IN_EXISTS: join order is the same, but the left IN operand refers to
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only the first table in the join order (Country), so there are much
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fewer rows to filter by subquery re-execution.
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EXPLAIN
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SELECT *
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FROM Country, City
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WHERE City.Country = Country.Code AND
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Country.SurfaceArea < 3000 AND Country.SurfaceArea > 10 AND
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(Country.Name IN
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(select Language from CountryLanguage where Percentage > 50) OR
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Country.name LIKE '%Island%');
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country ALL PRIMARY,SurfaceArea NULL NULL NULL 239 Using where
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1 PRIMARY City ref Country Country 3 world.Country.Code 17
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2 DEPENDENT SUBQUERY CountryLanguage index_subquery Percentage,Language Language 30 func 2 Using where
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SELECT *
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FROM Country, City
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WHERE City.Country = Country.Code AND
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Country.SurfaceArea < 3000 AND Country.SurfaceArea > 10 AND
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(Country.Name IN
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(select Language from CountryLanguage where Percentage > 50) OR
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Country.name LIKE '%Island%');
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Code Name SurfaceArea Population Capital ID Name Country population
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VGB Virgin Islands, British 151.00 21000 537 537 Road Town VGB 8000
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CYM Cayman Islands 264.00 38000 553 553 George Town CYM 19600
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COK Cook Islands 236.00 20000 583 583 Avarua COK 11900
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FRO Faroe Islands 1399.00 43000 901 901 Tórshavn FRO 14542
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CXR Christmas Island 135.00 2500 1791 1791 Flying Fish Cove CXR 700
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KIR Kiribati 726.00 83000 2256 2255 Bikenibeu KIR 5055
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KIR Kiribati 726.00 83000 2256 2256 Bairiki KIR 2226
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CCK Cocos (Keeling) Islands 14.00 600 2317 2316 Bantam CCK 503
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CCK Cocos (Keeling) Islands 14.00 600 2317 2317 West Island CCK 167
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MHL Marshall Islands 181.00 64000 2507 2507 Dalap-Uliga-Darrit MHL 28000
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NRU Nauru 21.00 12000 2728 2727 Yangor NRU 4050
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NRU Nauru 21.00 12000 2728 2728 Yaren NRU 559
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NFK Norfolk Island 36.00 2000 2806 2806 Kingston NFK 800
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PLW Palau 459.00 19000 2881 2881 Koror PLW 12000
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MNP Northern Mariana Islands 464.00 78000 2913 2913 Garapan MNP 9200
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TCA Turks and Caicos Islands 430.00 17000 3423 3423 Cockburn Town TCA 4800
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TUV Tuvalu 26.00 12000 3424 3424 Funafuti TUV 4600
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VIR Virgin Islands, U.S. 347.00 93000 4067 4067 Charlotte Amalie VIR 13000
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Q1.3:
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For the same reasons as in Q2 IN-EXISTS and MATERIALIZATION chosen
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for each respective subquery.
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EXPLAIN
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SELECT City.Name, Country.Name
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FROM City,Country
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WHERE City.Country = Country.Code AND
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Country.SurfaceArea < 30000 AND Country.SurfaceArea > 10 AND
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((Country.Code, Country.Name) IN
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(select Country, Language from CountryLanguage where Percentage > 50) AND
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Country.Population > 3000000
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OR
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(Country.Code, City.Name) IN
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(select Country, Language from CountryLanguage));
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country ALL PRIMARY,SurfaceArea NULL NULL NULL 239 Using where
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1 PRIMARY City ref Country Country 3 world.Country.Code 17 Using where
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3 MATERIALIZED CountryLanguage index PRIMARY,Language PRIMARY 33 NULL 984 Using index
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2 DEPENDENT SUBQUERY CountryLanguage unique_subquery PRIMARY,Percentage,Language PRIMARY 33 func,func 1 Using where
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SELECT City.Name, Country.Name
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FROM City,Country
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WHERE City.Country = Country.Code AND
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Country.SurfaceArea < 30000 AND Country.SurfaceArea > 10 AND
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((Country.Code, Country.Name) IN
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(select Country, Language from CountryLanguage where Percentage > 50) AND
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Country.Population > 3000000
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OR
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(Country.Code, City.Name) IN
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(select Country, Language from CountryLanguage));
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Name Name
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Kigali Rwanda
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2. NOT IN subqueries
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Q2.1:
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Number of cities that are not capitals in countries with small population.
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MATERIALIZATION is 50 times faster because the cost of each subquery
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re-execution is much higher than the cost of index lookups into the
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materialized subquery.
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EXPLAIN
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select count(*) from City
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where City.id not in (select capital from Country
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where capital is not null and population < 100000);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY City index NULL PRIMARY 4 NULL 4079 Using where; Using index
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2 MATERIALIZED Country ALL NULL NULL NULL NULL 239 Using where
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Q2.2e:
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Countries that speak French, but do not speak English
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IN-EXISTS because the outer query filters many rows, thus
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there are few lookups to make.
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EXPLAIN
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SELECT Country.Name
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FROM Country, CountryLanguage
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WHERE Code NOT IN (SELECT Country FROM CountryLanguage WHERE Language = 'English')
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AND CountryLanguage.Language = 'French'
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AND Code = Country;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY CountryLanguage ref PRIMARY,Language Language 30 const 19 Using index condition
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1 PRIMARY Country eq_ref PRIMARY PRIMARY 3 world.CountryLanguage.Country 1 Using where
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2 DEPENDENT SUBQUERY CountryLanguage unique_subquery PRIMARY,Language PRIMARY 33 func,const 1 Using index; Using where
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SELECT Country.Name
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FROM Country, CountryLanguage
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WHERE Code NOT IN (SELECT Country FROM CountryLanguage WHERE Language = 'English')
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AND CountryLanguage.Language = 'French'
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AND Code = Country;
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Name
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France
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Saint Pierre and Miquelon
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Belgium
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Burundi
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Guadeloupe
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Haiti
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Madagascar
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Martinique
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Mayotte
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French Polynesia
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Rwanda
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Sao Tome and Principe
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Switzerland
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New Caledonia
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Lebanon
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Mauritius
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Andorra
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Italy
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Luxembourg
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Q2.2m:
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Countries that speak French OR Spanish, but do not speak English
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MATERIALIZATION because the outer query filters less rows than Q5-a,
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so there are more lookups.
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set statement optimizer_switch='rowid_filter=off' for
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EXPLAIN
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SELECT Country.Name
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FROM Country, CountryLanguage
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WHERE Code NOT IN (SELECT Country FROM CountryLanguage WHERE Language = 'English')
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AND (CountryLanguage.Language = 'French' OR CountryLanguage.Language = 'Spanish')
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AND Code = Country;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY CountryLanguage range PRIMARY,Language Language 30 NULL 44 Using index condition; Rowid-ordered scan
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1 PRIMARY Country eq_ref PRIMARY PRIMARY 3 world.CountryLanguage.Country 1 Using where
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3 DEPENDENT SUBQUERY CountryLanguage unique_subquery PRIMARY,Language PRIMARY 33 func,const 1 Using index; Using where
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set statement optimizer_switch='rowid_filter=off' for
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SELECT Country.Name
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FROM Country, CountryLanguage
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WHERE Code NOT IN (SELECT Country FROM CountryLanguage WHERE Language = 'English')
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AND (CountryLanguage.Language = 'French' OR CountryLanguage.Language = 'Spanish')
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AND Code = Country;
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Name
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Andorra
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Argentina
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Bolivia
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Chile
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Costa Rica
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Dominican Republic
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Ecuador
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El Salvador
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Spain
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Guatemala
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Honduras
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Colombia
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Cuba
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Mexico
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Nicaragua
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Panama
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Paraguay
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Peru
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France
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Saint Pierre and Miquelon
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Uruguay
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Venezuela
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Belgium
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Burundi
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Guadeloupe
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Haiti
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Madagascar
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Martinique
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Mayotte
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French Polynesia
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Rwanda
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Sao Tome and Principe
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Switzerland
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New Caledonia
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Lebanon
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Mauritius
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Andorra
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Italy
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Luxembourg
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France
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Sweden
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Q2.3e:
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Not a very meaningful query that tests NOT IN.
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IN-EXISTS because the outer query is cheap enough to reexecute many times.
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EXPLAIN
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select count(*)
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from CountryLanguage
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where (Language, Country) NOT IN
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(SELECT City.Name, Country.Code
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FROM City LEFT JOIN Country ON (Country = Code and City.Population < 10000))
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AND Language IN ('English','Spanish');
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY CountryLanguage range Language Language 30 NULL 73 Using index condition; Using where; Rowid-ordered scan
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2 DEPENDENT SUBQUERY City ref CityName CityName 35 func 1 Using index condition
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2 DEPENDENT SUBQUERY Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using index
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select count(*)
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from CountryLanguage
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where (Language, Country) NOT IN
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(SELECT City.Name, Country.Code
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FROM City LEFT JOIN Country ON (Country = Code and City.Population < 10000))
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AND Language IN ('English','Spanish');
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count(*)
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88
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Q2.3m:
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MATERIALIZATION with the PARTIAL_MATCH_MERGE strategy, because the HAVING
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clause prevents the use of the index on City(Name), and in practice reduces
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radically the size of the temp table.
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EXPLAIN
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select count(*)
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from CountryLanguage
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where (Language, Country) NOT IN
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(SELECT City.Name, Country.Code
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FROM City LEFT JOIN Country ON (Country = Code)
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HAVING City.Name LIKE "Santa%");
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY CountryLanguage index NULL PRIMARY 33 NULL 984 Using where; Using index
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2 MATERIALIZED City ALL NULL NULL NULL NULL 4079
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2 MATERIALIZED Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using index
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select count(*)
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from CountryLanguage
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where (Language, Country) NOT IN
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(SELECT City.Name, Country.Code
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FROM City LEFT JOIN Country ON (Country = Code)
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HAVING City.Name LIKE "Santa%");
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count(*)
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984
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3. Subqueries with GROUP BY, HAVING, and aggregate functions
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Q3.1:
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Languages that are spoken in countries with 10 or 11 languages
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MATERIALIZATION is about 100 times faster than IN-EXISTS.
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EXPLAIN
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select count(*)
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from CountryLanguage
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where
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(Country, 10) IN (SELECT Code, COUNT(*) FROM CountryLanguage, Country
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WHERE Code = Country GROUP BY Code)
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OR
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(Country, 11) IN (SELECT Code, COUNT(*) FROM CountryLanguage, Country
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WHERE Code = Country GROUP BY Code)
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order by Country;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY CountryLanguage index NULL PRIMARY 33 NULL 984 Using where; Using index
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3 MATERIALIZED Country index PRIMARY PRIMARY 3 NULL 239 Using index
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3 MATERIALIZED CountryLanguage ref PRIMARY PRIMARY 3 world.Country.Code 4 Using index
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2 MATERIALIZED Country index PRIMARY PRIMARY 3 NULL 239 Using index
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2 MATERIALIZED CountryLanguage ref PRIMARY PRIMARY 3 world.Country.Code 4 Using index
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select count(*)
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from CountryLanguage
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where
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(Country, 10) IN (SELECT Code, COUNT(*) FROM CountryLanguage, Country
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WHERE Code = Country GROUP BY Code)
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OR
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(Country, 11) IN (SELECT Code, COUNT(*) FROM CountryLanguage, Country
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WHERE Code = Country GROUP BY Code)
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order by Country;
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count(*)
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102
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Q3.2:
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Countries whose capital is a city name that names more than one
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cities.
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MATERIALIZATION because the cost of single subquery execution is
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close to that of materializing the subquery.
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EXPLAIN
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select * from Country, City
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where capital = id and
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(City.name in (SELECT name FROM City
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GROUP BY name HAVING Count(*) > 2) OR
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capital is null);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country ALL NULL NULL NULL NULL 239 Using where
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1 PRIMARY City eq_ref PRIMARY PRIMARY 4 world.Country.Capital 1 Using where
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2 MATERIALIZED City index NULL CityName 35 NULL 4079 Using index
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select * from Country, City
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where capital = id and
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(City.name in (SELECT name FROM City
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GROUP BY name HAVING Count(*) > 2) OR
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capital is null);
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Code Name SurfaceArea Population Capital ID Name Country population
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BMU Bermuda 53.00 65000 191 191 Hamilton BMU 1200
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BOL Bolivia 1098581.00 8329000 194 194 La Paz BOL 758141
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CRI Costa Rica 51100.00 4023000 584 584 San José CRI 339131
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HKG Hong Kong 1075.00 6782000 937 937 Victoria HKG 1312637
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SYC Seychelles 455.00 77000 3206 3206 Victoria SYC 41000
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Q3.3: MATERIALIZATION is 25 times faster than IN-EXISTS
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EXPLAIN
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SELECT Name
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FROM Country
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WHERE Country.Code NOT IN
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(SELECT Country FROM City GROUP BY Name HAVING COUNT(Name) = 1);
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY Country ALL NULL NULL NULL NULL 239 Using where
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2 MATERIALIZED City ALL NULL NULL NULL NULL 4079 Using temporary
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SELECT Name
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FROM Country
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WHERE Country.Code NOT IN
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(SELECT Country FROM City GROUP BY Name HAVING COUNT(Name) = 1);
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Name
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Antigua and Barbuda
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Costa Rica
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Montserrat
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Norfolk Island
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Seychelles
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Antarctica
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Bouvet Island
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British Indian Ocean Territory
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South Georgia and the South Sandwich Islands
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Heard Island and McDonald Islands
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French Southern territories
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United States Minor Outlying Islands
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4. Subqueries in the SELECT and HAVING clauses
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Q4.1m:
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Capital information about very big cities
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MATERIALIZATION
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EXPLAIN
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select Name, City.id in (select capital from Country where capital is not null) as is_capital
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from City
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where City.population > 10000000;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY City range Population Population 5 NULL 3 Using index condition; Rowid-ordered scan
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2 MATERIALIZED Country ALL NULL NULL NULL NULL 239 Using where
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select Name, City.id in (select capital from Country where capital is not null) as is_capital
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from City
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where City.population > 10000000;
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Name is_capital
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Mumbai (Bombay) 0
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Q4.1e:
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IN-TO-EXISTS after adding an index to make the subquery re-execution
|
|
efficient.
|
|
create index CountryCapital on Country(capital);
|
|
EXPLAIN
|
|
select Name, City.id in (select capital from Country where capital is not null) as is_capital
|
|
from City
|
|
where City.population > 10000000;
|
|
id select_type table type possible_keys key key_len ref rows Extra
|
|
1 PRIMARY City range Population Population 5 NULL 3 Using index condition; Rowid-ordered scan
|
|
2 SUBQUERY Country index_subquery CountryCapital CountryCapital 5 func 2 Using index; Using where
|
|
select Name, City.id in (select capital from Country where capital is not null) as is_capital
|
|
from City
|
|
where City.population > 10000000;
|
|
Name is_capital
|
|
Mumbai (Bombay) 0
|
|
drop index CountryCapital on Country;
|
|
|
|
Q4.2:
|
|
MATERIALIZATION
|
|
EXPLAIN
|
|
SELECT City.Name, City.Population
|
|
FROM City JOIN Country ON City.Country = Country.Code
|
|
GROUP BY City.Name
|
|
HAVING City.Name IN (select Name from Country where population < 1000000);
|
|
id select_type table type possible_keys key key_len ref rows Extra
|
|
1 PRIMARY City ALL Country NULL NULL NULL 4079 Using temporary; Using filesort
|
|
1 PRIMARY Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using index
|
|
2 MATERIALIZED Country ALL Name NULL NULL NULL 239 Using where
|
|
Last_query_cost 5.934845
|
|
EXPLAIN
|
|
SELECT straight_join City.Name, City.Population
|
|
FROM Country JOIN City ON City.Country = Country.Code
|
|
GROUP BY City.Name
|
|
HAVING City.Name IN (select Name from Country where population < 1000000);
|
|
id select_type table type possible_keys key key_len ref rows Extra
|
|
1 PRIMARY Country index PRIMARY PRIMARY 3 NULL 239 Using index; Using temporary; Using filesort
|
|
1 PRIMARY City ref Country Country 3 world.Country.Code 17
|
|
2 MATERIALIZED Country ALL Name NULL NULL NULL 239 Using where
|
|
Last_query_cost 7.972882
|
|
EXPLAIN
|
|
SELECT City.Name, City.Population
|
|
FROM Country LEFT JOIN City ON City.Country = Country.Code
|
|
GROUP BY City.Name
|
|
HAVING City.Name IN (select Name from Country where population < 1000000);
|
|
id select_type table type possible_keys key key_len ref rows Extra
|
|
1 PRIMARY Country index NULL PRIMARY 3 NULL 239 Using index; Using temporary; Using filesort
|
|
1 PRIMARY City ref Country Country 3 world.Country.Code 17
|
|
2 MATERIALIZED Country ALL Name NULL NULL NULL 239 Using where
|
|
Last_query_cost 7.972882
|
|
SELECT City.Name, City.Population
|
|
FROM City JOIN Country ON City.Country = Country.Code
|
|
GROUP BY City.Name
|
|
HAVING City.Name IN (select Name from Country where population < 1000000);
|
|
Name Population
|
|
Djibouti 383000
|
|
Gibraltar 27025
|
|
Macao 437500
|
|
San Marino 2294
|
|
|
|
5. Subqueries with UNION
|
|
|
|
Q5.1:
|
|
EXPLAIN
|
|
SELECT * from City where (Name, 91) in
|
|
(SELECT Name, round(Population/1000)
|
|
FROM City
|
|
WHERE Country = "IND" AND Population > 2500000
|
|
UNION
|
|
SELECT Name, round(Population/1000)
|
|
FROM City
|
|
WHERE Country = "IND" AND Population < 100000);
|
|
id select_type table type possible_keys key key_len ref rows Extra
|
|
1 PRIMARY City ALL NULL NULL NULL NULL 4079 Using where
|
|
2 DEPENDENT SUBQUERY City ref Population,Country,CityName CityName 35 func 1 Using where
|
|
3 DEPENDENT UNION City ref Population,Country,CityName CityName 35 func 1 Using where
|
|
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
|
|
SELECT * from City where (Name, 91) in
|
|
(SELECT Name, round(Population/1000)
|
|
FROM City
|
|
WHERE Country = "IND" AND Population > 2500000
|
|
UNION
|
|
SELECT Name, round(Population/1000)
|
|
FROM City
|
|
WHERE Country = "IND" AND Population < 100000);
|
|
ID Name Country population
|
|
1359 Hassan IND 90803
|
|
1360 Ambala Sadar IND 90712
|
|
1361 Baidyabati IND 90601
|
|
set @@optimizer_switch='default';
|
|
drop database world;
|
|
|
|
|
|
TEST GROUP 2:
|
|
Tests of various combinations of optimizer switches, types of queries,
|
|
available indexes, column nullability, constness of tables/predicates.
|
|
=====================================================================
|
|
set optimizer_switch=default;
|
|
ALTER DATABASE test CHARACTER SET utf8mb4 COLLATE utf8mb4_uca1400_ai_ci;
|