drop table if exists t1,t2; create table t1 (i int, j int, empty_string char(10), bool char(1), d date); insert into t1 values (1,2,"","Y","2002-03-03"), (3,4,"","N","2002-03-04"), (5,6,"","Y","2002-03-04"), (7,8,"","N","2002-03-05"); select count(*) from t1 procedure analyse(); Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype count(*) 4 4 1 1 0 0 4.0000 0.0000 ENUM('4') NOT NULL select * from t1 procedure analyse(); Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype test.t1.i 1 7 1 1 0 0 4.0000 2.2361 ENUM('1','3','5','7') NOT NULL test.t1.j 2 8 1 1 0 0 5.0000 2.2361 ENUM('2','4','6','8') NOT NULL test.t1.empty_string 0 0 4 0 0.0000 NULL CHAR(0) NOT NULL test.t1.bool N Y 1 1 0 0 1.0000 NULL ENUM('N','Y') NOT NULL test.t1.d 2002-03-03 2002-03-05 10 10 0 0 10.0000 NULL ENUM('2002-03-03','2002-03-04','2002-03-05') NOT NULL select * from t1 procedure analyse(2); Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype test.t1.i 1 7 1 1 0 0 4.0000 2.2361 TINYINT(1) UNSIGNED NOT NULL test.t1.j 2 8 1 1 0 0 5.0000 2.2361 TINYINT(1) UNSIGNED NOT NULL test.t1.empty_string 0 0 4 0 0.0000 NULL CHAR(0) NOT NULL test.t1.bool N Y 1 1 0 0 1.0000 NULL ENUM('N','Y') NOT NULL test.t1.d 2002-03-03 2002-03-05 10 10 0 0 10.0000 NULL ENUM('2002-03-03','2002-03-04','2002-03-05') NOT NULL create table t2 select * from t1 procedure analyse(); select * from t2; Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype test.t1.i 1 7 1 1 0 0 4.0000 2.2361 ENUM('1','3','5','7') NOT NULL test.t1.j 2 8 1 1 0 0 5.0000 2.2361 ENUM('2','4','6','8') NOT NULL test.t1.empty_string 0 0 4 0 0.0000 NULL CHAR(0) NOT NULL test.t1.bool N Y 1 1 0 0 1.0000 NULL ENUM('N','Y') NOT NULL test.t1.d 2002-03-03 2002-03-05 10 10 0 0 10.0000 NULL ENUM('2002-03-03','2002-03-04','2002-03-05') NOT NULL drop table t1,t2; EXPLAIN SELECT 1 FROM (SELECT 1) a PROCEDURE ANALYSE(); id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY system NULL NULL NULL NULL 1 2 DERIVED NULL NULL NULL NULL NULL NULL NULL No tables used create table t1 (a int not null); create table t2 select * from t1 where 0=1 procedure analyse(); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `Field_name` varbinary(255) NOT NULL default '', `Min_value` varbinary(255) default NULL, `Max_value` varbinary(255) default NULL, `Min_length` bigint(11) NOT NULL default '0', `Max_length` bigint(11) NOT NULL default '0', `Empties_or_zeros` bigint(11) NOT NULL default '0', `Nulls` bigint(11) NOT NULL default '0', `Avg_value_or_avg_length` varbinary(255) NOT NULL default '', `Std` varbinary(255) default NULL, `Optimal_fieldtype` varbinary(64) NOT NULL default '' ) ENGINE=MyISAM DEFAULT CHARSET=latin1 select * from t1 where 0=1 procedure analyse(); Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype insert into t1 values(1); drop table t2; create table t2 select * from t1 where 0=1 procedure analyse(); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `Field_name` varbinary(255) NOT NULL default '', `Min_value` varbinary(255) default NULL, `Max_value` varbinary(255) default NULL, `Min_length` bigint(11) NOT NULL default '0', `Max_length` bigint(11) NOT NULL default '0', `Empties_or_zeros` bigint(11) NOT NULL default '0', `Nulls` bigint(11) NOT NULL default '0', `Avg_value_or_avg_length` varbinary(255) NOT NULL default '', `Std` varbinary(255) default NULL, `Optimal_fieldtype` varbinary(64) NOT NULL default '' ) ENGINE=MyISAM DEFAULT CHARSET=latin1 select * from t2; Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype insert into t2 select * from t1 procedure analyse(); select * from t2; Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype test.t1.a 1 1 1 1 0 0 1.0000 0.0000 ENUM('1') NOT NULL insert into t1 values(2); drop table t2; create table t2 select * from t1 where 0=1 procedure analyse(); show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `Field_name` varbinary(255) NOT NULL default '', `Min_value` varbinary(255) default NULL, `Max_value` varbinary(255) default NULL, `Min_length` bigint(11) NOT NULL default '0', `Max_length` bigint(11) NOT NULL default '0', `Empties_or_zeros` bigint(11) NOT NULL default '0', `Nulls` bigint(11) NOT NULL default '0', `Avg_value_or_avg_length` varbinary(255) NOT NULL default '', `Std` varbinary(255) default NULL, `Optimal_fieldtype` varbinary(64) NOT NULL default '' ) ENGINE=MyISAM DEFAULT CHARSET=latin1 select * from t2; Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype insert into t2 select * from t1 procedure analyse(); select * from t2; Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype test.t1.a 1 2 1 1 0 0 1.5000 0.5000 ENUM('1','2') NOT NULL drop table t1,t2; create table t1 (v varchar(128)); insert into t1 values ('abc'),('abc\'def\\hij\"klm\0opq'),('\''),('\"'),('\\'),('a\0'),('b\''),('c\"'),('d\\'),('\'b'),('\"c'),('\\d'),('a\0\0\0b'),('a\'\'\'\'b'),('a\"\"\"\"b'),('a\\\\\\\\b'),('\'\0\\\"'),('\'\''),('\"\"'),('\\\\'),('The\ZEnd'); select * from t1 procedure analyse(); Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype test.t1.v " \\ 1 19 0 0 3.7619 NULL ENUM('"','""','"c','\'\0\\"','\'','\'\'','\'b','a\0\0\0b','a\0','a""""b','a\'\'\'\'b','abc','abc\'def\\hij"klm\0opq','a\\\\\\\\b','b\'','c"','d\\','The\ZEnd','\\','\\d','\\\\') NOT NULL drop table t1; create table t1 (df decimal(5,1)); insert into t1 values(1.1); insert into t1 values(2.2); select * from t1 procedure analyse(); Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype test.t1.df 1.1 2.2 8 8 0 0 1.650000000 0.302500000 ENUM('1.1','2.2') NOT NULL drop table t1; create table t1 (d double); insert into t1 values (100000); select * from t1 procedure analyse (1,1); Field_name Min_value Max_value Min_length Max_length Empties_or_zeros Nulls Avg_value_or_avg_length Std Optimal_fieldtype test.t1.d 100000 100000 6 6 0 0 100000 0 MEDIUMINT(6) UNSIGNED NOT NULL drop table t1;