explain someSql; possible_keys show useable keysexplain select a from b use index (c) where xxx ;show index from tableA;create index someIndex on someTable(someColumn);drop index someIndex on someTable;*************************** 1. row *************************** id: 1 select_type: SIMPLE table: some table partitions: NULL type: ALLpossible_keys: PRIMARY ...
2021/10/18
2021/04/22
insert ignore
INSERT IGNORE INTO users (userid,username) VALUES (2,'swan'),(4,'bear') ;---
Query OK, 1 row affected, 1 warning (0.02 sec)
Records: 2 Duplicates: 1 Warnings:...
mysqlのorder by fieldで指定のID順に並べる
select * from icons
where id in(4, 5, 6)
order by field(id, 5, 4, 6)
=>
mysql> select * from icons where id in(4, 5, 6) order by field(id, 5, 4, ...