Mysql delete操做

如下摘自官方文档：https://dev.mysql.com/doc/refman/5.7/en/insert.html

语法：

    

DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM 
    [PARTITION (,...)]
    [WHERE ]
    [ORDER BY ...]
    [LIMIT ]


性能:
   When you do not need to know the number of deleted rows, the  statement is a faster way to empty a table than a statement with no  clause. Unlike ,  cannot be used within a transaction or if you have a lock on the table. SeeSection 14.1.34, “TRUNCATE TABLE Syntax” and Section 14.3.5, “LOCK TABLES and UNLOCK TABLES Syntax”.
   简单理解是：truncate 在不锁表的状况下，很快：

   若是想用delete删除快点：
    The time required to delete individual rows in a  table is exactly proportional to the number of indexes. To delete rows more quickly, you can increase the size of the key cache by increasing the  system variable
    能够配置的key_buffer_size大小
多表删除：
(1)不带别名tbl_namepartition_namewhere_conditionrow_countTRUNCATE TABLEDELETEWHEREDELETETRUNCATE TABLEMyISAMkey_buffer_size

DELETE t1, t2 FROM t1 INNER JOIN t2 INNER JOIN t3
WHERE t1.id=t2.id AND t2.id=t3.id;

Or:

DELETE FROM t1, t2 USING t1 INNER JOIN t2 INNER JOIN t3
WHERE t1.id=t2.id AND t2.id=t3.id;
(2)带别名：必须写别名：

  If you declare an alias for a table, you must use the alias when referring to the table:

DELETE t1 FROM test AS t1, test2 WHERE ...

Correct:

DELETE a1, a2 FROM t1 AS a1 INNER JOIN t2 AS a2
WHERE a1.id=a2.id;

DELETE FROM a1, a2 USING t1 AS a1 INNER JOIN t2 AS a2
WHERE a1.id=a2.id;

二、删除mysql 中重复记录，并保留一条

DELETE FROM `tb_phones` WHERE id NOT IN(SELECT * FROM(SELECT id FROM `tb_phones` GROUP BY phone)AS b);