sql优化

SELECT DISTINCT
t1.no
FROM
tab1e1 t1,
tab1e2 t2
WHERE
t1.code = t2.code

0.01 s

SELECT
t.no
FROM
(
SELECT DISTINCT
t1.no
FROM
table1 t1,
table2 t2
WHERE
t1.code = t2.code
) t limit 0,10;

0.29s

前面查出来的数据， 进行limit 遍历 所以慢

优化为

SELECT
t.no
FROM
(
SELECT DISTINCT
t1.no
FROM
table1 t1,
table2 t2
WHERE
t1.code = t2.code limit 0,10
) t ;

0.01s