DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (
id INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT, 
gender CHAR(1),
name VARCHAR(20)
);
SELECT SUM(DISTINCT LENGTH(name)) s1 FROM t1;
s1
NULL
INSERT INTO t1 (gender, name) VALUES (NULL, NULL);
INSERT INTO t1 (gender, name) VALUES (NULL, NULL);
INSERT INTO t1 (gender, name) VALUES (NULL, NULL);
SELECT SUM(DISTINCT LENGTH(name)) s1 FROM t1;
s1
NULL
INSERT INTO t1 (gender, name) VALUES ('F', 'Helen'), ('F', 'Anastasia'),
('F', 'Katherine'), ('F', 'Margo'), ('F', 'Magdalene'), ('F', 'Mary');
CREATE TABLE t2 SELECT name FROM t1;
SELECT (SELECT SUM(DISTINCT LENGTH(name)) FROM t1) FROM t2;
(SELECT SUM(DISTINCT LENGTH(name)) FROM t1)
18
18
18
18
18
18
18
18
18
DROP TABLE t2;
INSERT INTO t1 (gender, name) VALUES ('F', 'Eva'), ('F', 'Sofia'),
('F', 'Sara'), ('F', 'Golda'), ('F', 'Toba'), ('F', 'Victory'),
('F', 'Faina'), ('F', 'Miriam'), ('F', 'Beki'), ('F', 'America'),
('F', 'Susan'), ('F', 'Glory'), ('F', 'Priscilla'), ('F', 'Rosmary'),
('F', 'Rose'), ('F', 'Margareth'), ('F', 'Elizabeth'), ('F', 'Meredith'),
('F', 'Julie'), ('F', 'Xenia'), ('F', 'Zena'), ('F', 'Olga'),
('F', 'Brunhilda'), ('F', 'Nataly'), ('F', 'Lara'), ('F', 'Svetlana'),
('F', 'Grethem'), ('F', 'Irene');
SELECT
SUM(DISTINCT LENGTH(name)) s1,
SUM(DISTINCT SUBSTRING(NAME, 1, 3)) s2,
SUM(DISTINCT LENGTH(SUBSTRING(name, 1, 4))) s3
FROM t1;
s1	s2	s3
42	0	7
SELECT
SUM(DISTINCT LENGTH(g1.name)) s1,
SUM(DISTINCT SUBSTRING(g2.name, 1, 3)) s2,
SUM(DISTINCT LENGTH(SUBSTRING(g3.name, 1, 4))) s3
FROM t1 g1, t1 g2, t1 g3;
s1	s2	s3
42	0	7
SELECT
SUM(DISTINCT LENGTH(g1.name)) s1,
SUM(DISTINCT SUBSTRING(g2.name, 1, 3)) s2,
SUM(DISTINCT LENGTH(SUBSTRING(g3.name, 1, 4))) s3
FROM t1 g1, t1 g2, t1 g3 GROUP BY LENGTH(SUBSTRING(g3.name, 5, 10));
s1	s2	s3
42	0	NULL
42	0	7
42	0	4
42	0	4
42	0	4
42	0	4
42	0	4
SELECT SQL_BUFFER_RESULT
SUM(DISTINCT LENGTH(name)) s1,
SUM(DISTINCT SUBSTRING(NAME, 1, 3)) s2,
SUM(DISTINCT LENGTH(SUBSTRING(name, 1, 4))) s3
FROM t1;
s1	s2	s3
42	0	7
SELECT SQL_BUFFER_RESULT
SUM(DISTINCT LENGTH(g1.name)) s1,
SUM(DISTINCT SUBSTRING(g2.name, 1, 3)) s2,
SUM(DISTINCT LENGTH(SUBSTRING(g3.name, 1, 4))) s3
FROM t1 g1, t1 g2, t1 g3 GROUP BY LENGTH(SUBSTRING(g3.name, 5, 10));
s1	s2	s3
42	0	NULL
42	0	7
42	0	4
42	0	4
42	0	4
42	0	4
42	0	4
SET @l=1;
UPDATE t1 SET name=CONCAT(name, @l:=@l+1);
SELECT SUM(DISTINCT RIGHT(name, 1)) FROM t1;
SUM(DISTINCT RIGHT(name, 1))
45
SELECT SUM(DISTINCT id) FROM t1;
SUM(DISTINCT id)
703
SELECT SUM(DISTINCT id % 11) FROM t1;
SUM(DISTINCT id % 11)
55
DROP TABLE t1;
CREATE TABLE t1 (id INTEGER);
CREATE TABLE t2 (id INTEGER);
INSERT INTO t1 (id) VALUES (1), (1), (1),(1);
INSERT INTO t2 (id) SELECT id FROM t1;
INSERT INTO t1 (id) SELECT id FROM t2;
/* 8 */
INSERT INTO t1 (id) SELECT id FROM t2;
/* 12 */
INSERT INTO t1 (id) SELECT id FROM t2;
/* 16 */
INSERT INTO t1 (id) SELECT id FROM t2;
/* 20 */
INSERT INTO t1 (id) SELECT id FROM t2;
/* 24 */
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+1 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+2 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+4 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+8 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+16 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+32 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+64 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+128 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+256 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+512 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+1024 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+2048 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+4096 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 (id) SELECT id+8192 FROM t1;
INSERT INTO t1 SELECT id FROM t2;
DELETE FROM t2;
INSERT INTO t2 SELECT id FROM t1 ORDER BY id*rand();
SELECT SUM(DISTINCT id) sm FROM t1;
sm
134225920
SELECT SUM(DISTINCT id) sm FROM t2;
sm
134225920
SELECT SUM(DISTINCT id) sm FROM t1 group by id % 13;
sm
10327590
10328851
10330112
10331373
10332634
10317510
10318770
10320030
10321290
10322550
10323810
10325070
10326330
SET max_heap_table_size=16384;
SHOW variables LIKE 'max_heap_table_size';
Variable_name	Value
max_heap_table_size	16384
SELECT SUM(DISTINCT id) sm FROM t1;
sm
134225920
SELECT SUM(DISTINCT id) sm FROM t2;
sm
134225920
SELECT SUM(DISTINCT id) sm FROM t1 GROUP BY id % 13;
sm
10327590
10328851
10330112
10331373
10332634
10317510
10318770
10320030
10321290
10322550
10323810
10325070
10326330
DROP TABLE t1;
DROP TABLE t2;