我的查询似乎与http://dev.mysql.md/doc/refman/5.1/en/in-subquery-optimization.html的示例非常相似,但不幸的是,本手册中的收据对我不起作用。
当我单独运行它们时,内部和外部查询都使用索引,但是当我运行整个查询时,外部查询会扫描整个表...
的MySQL>解释选择smsId FROM SMSDelivery WHERE smsId IN(SELECT smsId FROM SMS WHERE phoneNumber ='123456'或fromUser ='5678p'or toUser ='5124p')\ G
*************************** 1. row ***************************
id: 1
select_type: PRIMARY
table: SMSDelivery
type: index
possible_keys: NULL
key: FK75C784D70BE5EC9
key_len: 4
ref: NULL
rows: 1337017
Extra: Using where; Using index
*************************** 2. row ***************************
id: 2
select_type: DEPENDENT SUBQUERY
table: SMS
type: unique_subquery
possible_keys: PRIMARY,phoneNumber,fromUser,toUser
key: PRIMARY
key_len: 4
ref: func
rows: 1
Extra: Using where
2 rows in set (0.00 sec)
答案 0 :(得分:0)
EXPLAIN
SELECT
sd.*
FROM
SMSDelivery sd
INNER JOIN
(
SELECT smsId FROM SMS WHERE phoneNumber='123456' OR fromUser='5678p' OR toUser='5124p'
) s ON sd.smsId = s.smsId;