我在有许多嵌套子句的查询中遇到缓慢的问题。
查询如下:
select SA0_.sid as stid from table_starea SA0_ left outer join table_arcons AC1_ on SA0_.acid=AC1_.acid where SA0_.sid in (select SB1_.sid from table_arstaff AC0_ left outer join table_stf SB1_ on AC0_.sid=SB1_.sid left outer join table_stfgr SG2_ on SB1_.sgid=SG2_.sgid where AC0_.acid in (select AC1_.acid from table_starea SA0_ left outer join table_arcons AC1_ on SA0_.acid=AC1_.acid where SA0_.sid in (select SB1_.sid from table_arstaff AC0_ left outer join table_stf SB1_ on AC0_.sid=SB1_.sid left outer join table_stfgr SG2_ on SB1_.sgid=SG2_.sgid where AC0_.acid in (select AC1_.acid from table_starea SA0_ left outer join table_arcons AC1_ on SA0_.acid=AC1_.acid where SA0_.sid in (select SB1_.sid from table_arstaff AC0_ left outer join table_stf SB1_ on AC0_.sid=SB1_.sid left outer join table_stfgr SG2_ on SB1_.sgid=SG2_.sgid where AC0_.acid in (select AC1_.acid from table_starea SA0_ left outer join table_arcons AC1_ on SA0_.acid=AC1_.acid where SA0_.sid in (select SB1_.sid from table_arstaff AC0_ left outer join table_stf SB1_ on AC0_.sid=SB1_.sid left outer join table_stfgr SG2_ on SB1_.sgid=SG2_.sgid where AC0_.acid in (select AC1_.acid from table_starea SA0_ left outer join table_arcons AC1_ on SA0_.acid=AC1_.acid where SA0_.sid in (select SB1_.sid from table_arstaff AC0_ left outer join table_stf SB1_ on AC0_.sid=SB1_.sid left outer join table_stfgr SG2_ on SB1_.sgid=SG2_.sgid where AC0_.acid in (select AC1_.acid from table_starea SA0_ left outer join table_arcons AC1_ on SA0_.acid=AC1_.acid where SA0_.sid in (select SB1_.sid from table_arstaff AC0_ left outer join table_stf SB1_ on AC0_.sid=SB1_.sid left outer join table_stfgr SG2_ on SB1_.sgid=SG2_.sgid where AC0_.acid=19)))))))))));
我检查了相同的解释，发现如下:
+----+--------------+-------------------+------------+------------+----------------------------------------+---------------------+---------+----------------------------------------------------+------+----------+--------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+--------------+-------------------+------------+------------+----------------------------------------+---------------------+---------+----------------------------------------------------+------+----------+--------------------------+
| 1 | SIMPLE | <subquery2> | NULL | ALL | NULL | NULL | NULL | NULL | NULL | 100.00 | Using where |
| 1 | SIMPLE | SA0_ | NULL | ref | table_starea_ix01 | table_starea_ix01 | 5 | <subquery2>.sid | 1 | 100.00 | Using index |
| 1 | SIMPLE | AC1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SA0_.acid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | AC0_ | NULL | ref | table_arstaff_ix01,tab_attach_fk2 | table_arstaff_ix01 | 4 | const | 4 | 100.00 | Using where; Using index |
| 2 | MATERIALIZED | SB1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.AC0_.sid | 1 | 100.00 | NULL |
| 2 | MATERIALIZED | SG2_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SB1_.sgid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | SA0_ | NULL | ref | FKFA890976F203761F,table_starea_ix01 | table_starea_ix01 | 5 | ain2013Realdb.AC0_.sid | 1 | 100.00 | Using where; Using index |
| 2 | MATERIALIZED | AC1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SA0_.acid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | AC0_ | NULL | ref | table_arstaff_ix01,tab_attach_fk2 | table_arstaff_ix01 | 4 | ain2013Realdb.SA0_.acid | 2 | 100.00 | Using where; Using index |
| 2 | MATERIALIZED | SB1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.AC0_.sid | 1 | 100.00 | NULL |
| 2 | MATERIALIZED | SG2_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SB1_.sgid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | SA0_ | NULL | ref | FKFA890976F203761F,table_starea_ix01 | table_starea_ix01 | 5 | ain2013Realdb.AC0_.sid | 1 | 100.00 | Using where; Using index |
| 2 | MATERIALIZED | AC1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SA0_.acid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | AC0_ | NULL | ref | table_arstaff_ix01,tab_attach_fk2 | table_arstaff_ix01 | 4 | ain2013Realdb.SA0_.acid | 2 | 100.00 | Using index |
| 2 | MATERIALIZED | SB1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.AC0_.sid | 1 | 100.00 | NULL |
| 2 | MATERIALIZED | SG2_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SB1_.sgid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | SA0_ | NULL | ref | FKFA890976F203761F,table_starea_ix01 | table_starea_ix01 | 5 | ain2013Realdb.AC0_.sid | 1 | 100.00 | Using where; Using index |
| 2 | MATERIALIZED | AC1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SA0_.acid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | AC0_ | NULL | ref | table_arstaff_ix01,tab_attach_fk2 | table_arstaff_ix01 | 4 | ain2013Realdb.SA0_.acid | 2 | 100.00 | Using where; Using index |
| 2 | MATERIALIZED | SB1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.AC0_.sid | 1 | 100.00 | NULL |
| 2 | MATERIALIZED | SG2_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SB1_.sgid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | SA0_ | NULL | ref | FKFA890976F203761F,table_starea_ix01 | table_starea_ix01 | 5 | ain2013Realdb.AC0_.sid | 1 | 100.00 | Using where; Using index |
| 2 | MATERIALIZED | AC1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SA0_.acid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | AC0_ | NULL | ref | table_arstaff_ix01,tab_attach_fk2 | table_arstaff_ix01 | 4 | ain2013Realdb.SA0_.acid | 2 | 100.00 | Using index |
| 2 | MATERIALIZED | SB1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.AC0_.sid | 1 | 100.00 | NULL |
| 2 | MATERIALIZED | SG2_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SB1_.sgid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | SA0_ | NULL | ref | FKFA890976F203761F,table_starea_ix01 | table_starea_ix01 | 5 | ain2013Realdb.AC0_.sid | 1 | 100.00 | Using where; Using index |
| 2 | MATERIALIZED | AC1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SA0_.acid | 1 | 100.00 | Using index |
| 2 | MATERIALIZED | AC0_ | NULL | ref | table_arstaff_ix01,tab_attach_fk2 | table_arstaff_ix01 | 4 | ain2013Realdb.SA0_.acid | 2 | 100.00 | Using index |
| 2 | MATERIALIZED | SB1_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.AC0_.sid | 1 | 100.00 | NULL |
| 2 | MATERIALIZED | SG2_ | NULL | eq_ref | PRIMARY | PRIMARY | 4 | ain2013Realdb.SB1_.sgid | 1 | 100.00 | Using index |
+----+--------------+-------------------+------------+------------+----------------------------------------+---------------------+---------+----------------------------------------------------+------+----------+--------------------------+
有人可以提出一个解决方案来使该查询快速执行吗？
我使用 INNER JOIN 重写了查询，如下所示:
选择 SA0_.sid 作为 stid from table_starea SA0_ left external join table_arcons AC1_ on SA0_.acid=AC1_.acid 其中 SA0_.sid in (select different sid from ((select SB1_.sid, AC0_.acid from table_arstaff AC0_ left external)在 AC0_.sid=SB1_.sid 上连接 table_stf SB1_ 在 SB1_.sgid=SG2_.sgid 上左外连接 table_stfgr SG2_ 在 SB1_.sgid=SG2_.sgid 上) TAB19 INNER JOIN(从 ((从 table_starea SA0_ 左外连接 table_arcons AC1_ 选择 AC1_.acid,SA0_.sid) SA0_.acid=AC1_.acid) TAB17 INNER JOIN (select sid from ((select SB1_.sid, AC0_.acid from table_arstaff AC0_ 左外连接 table_stf SB1_ 上 AC0_.sid=SB1_.sid 左外连接 table_stfgr SG2_ 上 SB1_。 sgid=SG2_.sgid) TAB15 INNER JOIN (selectacid from ((select AC1_.acid, SA0_.sid from table_starea SA0_ left external join table_arcons AC1_ on SA0_.acid=AC1_.acid) TAB13 INNER JOIN (select sid from ((select SB1_.sid, AC0_.acid 来自 table_arstaff AC0_ 左外连接 table_stf SB1_ 在 AC0_.sid=SB1_.sid 上左外连接 table_stfgr SG2_ 在 SB1_.sgid=SG2_.sgid) TAB11 INNER JOIN (从 ((select AC1_.acid , SA0_.sid from table_starea SA0_ 左外连接 table_arcons AC1_ on SA0_.acid=AC1_.acid) TAB9 INNER JOIN (select sid from ((select SB1_.sid, AC0_.acid from table_arstaff AC0_ 左外连接 table_stf SB1_ on AC0_.sid =SB1_.sid SB1_.sgid=SG2_.sgid 上的左外连接 table_stfgr SG2_) TAB7 INNER JOIN (select Acid from ((select AC1_.acid, SA0_.sid from table_starea SA0_ 左外连接 SA0_.acid=AC1_ 上的 table_arcons AC1_。 Acid) TAB5 INNER JOIN (select sid from (select SB1_.sid, AC0_.acid from table_arstaff AC0_左外连接 table_stf SB1_ on AC0_.sid=SB1_.sid left外连接 table_stfgr SG2_ on SB1_.sgid=SG2_.sgid) TAB3 INNER JOIN(从 table_starea SA0_ 左外连接 table_arcons AC1_ 上选择 AC1_.acid、SA0_.sid SA0_.acid=AC1_.acid) TAB2 INNER JOIN(从 table_arstaff AC0_ 左外连接 table_stf SB1_ 在 AC0_ 上选择 SB1_.sid。 sid=SB1_.sid 左外连接 table_stfgr SB1_.sgid=SG2_.sgid 上的 SG2_，其中 AC0_.acid=19) TAB1 ON TAB2.sid = TAB1.sid) TAB4 on TAB3.acid = TAB4.acid) TAB6 on TAB5.sid = TAB6.sid)) TAB8 上 TAB7.acid = TAB8.acid)) TAB10 上 TAB9.sid = TAB10.sid)) TAB12 上 TAB11.acid = TAB12.acid)) TAB14 上 TAB13.sid = TAB14.sid)) TAB16 上的 TAB15.acid = TAB16.acid)) TAB18 上的 TAB17.sid = TAB18.sid)) TAB20 上的 TAB19.acid = TAB20.acid));
这会带来优化吗？
最佳答案
关于性能的第一个建议..在大多数性能 INNER JOIN 子句中，每个 IN 子句都可以轻松更改，例如，对于更深的嵌套级别，您可以更改代码
....
select AC1_.acid
from table_starea SA0_
left outer join table_arcons AC1_ on SA0_.acid=AC1_.acid
where SA0_.sid in (
select SB1_.sid
from table_arstaff AC0_
left outer join table_stf SB1_ on AC0_.sid=SB1_.sid
left outer join table_stfgr SG2_ on SB1_.sgid=SG2_.sgid
where AC0_.acid=19 )
....)))))))));
与
......
select AC1_.acid
from table_starea SA0_
left outer join table_arcons AC1_ on SA0_.acid=AC1_.acid
) t2 on AC0_.acid = t2.acid
INNER JOIN (
select SB1_.sid
from table_arstaff AC0_
left outer join table_stf SB1_ on AC0_.sid=SB1_.sid
left outer join table_stfgr SG2_ on SB1_.sgid=SG2_.sgid
where AC0_.acid=19
) t1 on t1.sid = SA0_.sid
....)))))))));
结果是相同的，但内部联接应该更快..
你可以从更深层次开始重构你的代码，并用相应的 INNER JOIN 逐一重构所有 IN 子句
关于mysql - 具有许多嵌套子句的查询速度缓慢，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51965501/