标签：des style blog http color io os ar 使用
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: 0 mysql> 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
标签：des style blog http color io os ar 使用
原文地址：http://www.cnblogs.com/gsblog/p/4045251.html
