《高性能MySQL》 里面提及用in这种方式可以有效的替代一定的range查询,提升查询效率,因为在一条索引里面,range字段后面的部分是不生效的(ps.需要考虑 ICP)。MySQL优化器将in这种方式转化成 n*m 种组合进行查询,最终将返回值合并,有点类似union但是更高效。
1 row in set (0.00 sec) root@localhost 16:22:06 [ultrax]> SELECT sql_no_cache * FROM pre_forum_post WHERE tid=7932552 AND `invisible` IN('0','-2') ORDER BY dateline DESC LIMIT 10; ... 10 rows in set (0.40 sec) root@localhost 16:23:55 [ultrax]> SELECT sql_no_cache * ...
| 1 | SIMPLE | pre_forum_post | range | PRIMARY,displayorder,first,mul_test,idx_1 | displayorder | 4 | NULL | 54 | Using index condition; Using filesort | +---+---+---+---+---+---+---+---+---+---+ 1 row in set (0.00 sec) MySQL优化器认为...
root@localhost16:22:06[ultrax]>SELECTsql_no_cache*FROMpre_forum_postWHEREtid=7932552AND`invisible`IN('0','-2')ORDERBYdatelineDESCLIMIT10; ...10rowsinset(0.40sec) root@localhost16:23:55[ultrax]>SELECTsql_no_cache*FROMpre_forum_post force index (idx_1)WHEREtid=7932552AND`invisible`IN('...
《高性能MySQL》里面提及用in这种方式可以有效的替代一定的range查询,提升查询效率,因为在一条索引里面,range字段后面的部分是不生效的(ps.需要考虑 ICP)。MySQL优化器将in这种方式转化成 n*m 种组合进行查询,最终将返回值合并,有点类似union但是更高效。
Dimconn1AsNewConnectionWithconn1.Provider="Microsoft.ACE.OLEDB.12.0".ConnectionString="Data Source="&ThisWorkbook.FullName&";Extended Properties=""Excel 12.0 Macro;HDR=Yes;IMEX=1""".OpenEndWith'need lot of braskets to make multiple left join with string condition work lolSQL=" Select a.[Port...
The conditionkey_part1= 1defines this interval: (1,-inf,-inf)<=(key_part1,key_part2,key_part3)<(1,+inf,+inf) The interval covers the 4th, 5th, and 6th tuples in the preceding data set and can be used by the range access method. ...
KEY `idx_condition_id_operate_time` (`condition_id`,`operate_time`) USING BTREE COMMENT '索引', KEY `idx_operate_time` (`operate_time`) USING BTREE COMMENT '索引', KEY `idx_batch_id` (`batch_id`) ) ENGINE=InnoDB AUTO_INCREMENT=1037560 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicod...
A range condition is a search condition with a comparison predicate or a BETWEEN predicate. The SQL Optimizer can only evaluate range conditions that satisfy the following restrictions: In the range condition, only the comparison operators < | <= | => | > and the BETWEEN operator are used. ...
RANGE CONDITION FOR KEYは、SQLオプティマイザの検索方針です。 基本テーブルの一部のみが検索されます。開始キーと停止キーであることが判明しているキーを使用して範囲が制限されます。 以下の条件の1つが満たされる場合、この検索方針が選択されます。