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update and的坑
开发那边抛出个有意思的问题，下面的现象如何解释呢？
mysql> select * from A;+------+------+| t1 | t2 |+------+------+| 1 | 1 | | 2 | 2 | | 3 | 3 | +------+------+3 rows in set (0.00 sec)mysql> update A set t1=0 and t2=5; Query OK, 3 rows affected (0.00 sec)Rows matched: 3 Changed: 3 Warnings: 0mysql> select * from A; +------+------+| t1 | t2 |+------+------+| 0 | 1 | | 0 | 2 | | 0 | 3 | +------+------+3 rows in set (0.00 sec)update 语句 and 怎么解释？
Update的语法是：
UPDATE [LOW_PRIORITY] [IGNORE] table_reference SET col_name1={expr1|DEFAULT} [, col_name2={expr2|DEFAULT}] ... [WHERE where_condition] [ORDER BY ...] [LIMIT row_count]Multiple-table syntax:UPDATE [LOW_PRIORITY] [IGNORE] table_references SET col_name1={expr1|DEFAULT} [, col_name2={expr2|DEFAULT}] ... [WHERE where_condition]
select的语法：
Name: ‘SELECT‘Description:Syntax:SELECT [ALL | DISTINCT | DISTINCTROW ] [HIGH_PRIORITY] [STRAIGHT_JOIN] [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT] [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS] select_expr [, select_expr ...] [FROM table_references [PARTITION partition_list] [WHERE where_condition] [GROUP BY {col_name | expr | position} [ASC | DESC], ... [WITH ROLLUP]] [HAVING where_condition] [ORDER BY {col_name | expr | position} [ASC | DESC], ...] [LIMIT {[offset,] row_count | row_count OFFSET offset}] [PROCEDURE procedure_name(argument_list)] [INTO OUTFILE ‘file_name‘ [CHARACTER SET charset_name] export_options | INTO DUMPFILE ‘file_name‘ | INTO var_name [, var_name]] [FOR UPDATE | LOCK IN SHARE MODE]]
update语法是set后面以逗号区分
mysql> select * from test where t1=0 and t2=5;
Empty set (0.00 sec)
使用and被解析成 t1=0 and t2=5 把后面作为一个整体，值变成0了
变成这样了，update A set t1=(0 and t2=5)，t2==5 and 0
换种写法更加明白了
先记录下，后面整体再整理！！！
update and的坑
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