CREATE TABLE t1 (b int(2) zerofill, c int(2) zerofill);
INSERT INTO t1 (b,c) VALUES (1,2), (1,1), (2,2);
SELECT CONCAT(b,c), CONCAT(b,c) = '0101' FROM t1;
CONCAT(b,c) CONCAT(b,c) = '0101'
0102 0
0101 1
0202 0
EXPLAIN EXTENDED SELECT b,c FROM t1 WHERE b = 1 AND CONCAT(b,c) = '0101';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using where
Warnings:
Note 1003 select `test`.`t1`.`b` AS `b`,`test`.`t1`.`c` AS `c` from `test`.`t1` where ((`test`.`t1`.`b` = 1) and (concat(_binary'01',`test`.`t1`.`c`) = _latin1'0101'))
SELECT b,c FROM t1 WHERE b = 1 AND CONCAT(b,c) = '0101';
b c
01 01
CREATE TABLE t2 (a int);
INSERT INTO t2 VALUES (1),(2);
SELECT a,
(SELECT COUNT(*) FROM t1
WHERE b = t2.a AND CONCAT(b,c) = CONCAT('0',t2.a,'01')) x
FROM t2 ORDER BY a;
a x
1 1
2 0
EXPLAIN EXTENDED
SELECT a,
(SELECT COUNT(*) FROM t1
WHERE b = t2.a AND CONCAT(b,c) = CONCAT('0',t2.a,'01')) x
FROM t2 ORDER BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using filesort
2 DEPENDENT SUBQUERY t1 ALL NULL NULL NULL NULL 3 Using where
Warnings:
Note 1276 Field or reference 'test.t2.a' of SELECT #2 was resolved in SELECT #1
Note 1276 Field or reference 'test.t2.a' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`t2`.`a` AS `a`,(select count(0) AS `COUNT(*)` from `test`.`t1` where ((`test`.`t1`.`b` = `test`.`t2`.`a`) and (concat(`test`.`t1`.`b`,`test`.`t1`.`c`) = concat(_latin1'0',`test`.`t2`.`a`,_latin1'01')))) AS `x` from `test`.`t2` order by `test`.`t2`.`a`