如何解决mysql多个字段update时错误使用and连接字段的问题
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执行语句一
update spoken set book_id = 2 and unit_id = 14 and article_id = 47409 where id = 284989;
结果为只将book_id字段值更新为0,其他字段都没有更改
mysql> select id,book_id,unit_id,article_id from spoken;
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 5 | 55 | 55555 |
+--------+---------+---------+------------+
1 row in set (0.00 sec)
mysql> update spoken set book_id = 2 and unit_id = 14 and article_id = 47409 where id = 284989;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select id,book_id,unit_id,article_id from spoken;
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 0 | 55 | 55555 |
+--------+---------+---------+------------+
1 row in set (0.00 sec)
执行语句二
update spoken set book_id = 2,unit_id = 14,article_id = 47409 where id = 284989;（正常语句）
三个字段值都变更为给定值，
mysql> select id,book_id,unit_id,article_id from spoken;
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 0 | 55 | 55555 |
+--------+---------+---------+------------+
1 row in set (0.00 sec)
mysql> update spoken set book_id = 2,unit_id = 14,article_id = 47409 where id = 284989;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select id,book_id,unit_id,article_id from spoken;
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 2 | 14 | 47409 |
+--------+---------+---------+------------+
1 row in set (0.00 sec)
执行语句三
update spoken set book_id = 2 and unit_id = 14 and article_id = 47409 where id = 284989;
只将第一个字段变更为1
mysql> select id,book_id,unit_id,article_id from spoken;
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 2 | 14 | 47409 |
+--------+---------+---------+------------+
1 row in set (0.00 sec)
mysql> update spoken set book_id = 2 and unit_id = 14 and article_id = 47409 where id = 284989;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select id,book_id,unit_id,article_id from spoken;
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 1 | 14 | 47409 |
+--------+---------+---------+------------+
1 row in set (0.00 sec)
分析，
1、正常的update语法为语句二，更新多个字段的值，多个字段之间使用逗号“，”分隔。
2、但问题语句一和问题语句三更新多个字段的值使用and ，分隔多个字段；
且语句一将book_id变更为，语句三将book_id变更为1；
一、问题语句一
update spoken set book_id = 2 and unit_id = 14 and article_id = 47409 where id = 284989;
等价于
update spoken set book_id = (2 and unit_id = 14 and article_id = 47409) where id = 284989;
等价于
update spoken set book_id = (2 and (unit_id = 14) and (article_id = 47409)) where id = 284989;
相当于将book_id的值更新为下面语句的值
select 2 and (unit_id = 14) and (article_id = 47409) from spoken where id = 284989;
该语句由三个表达式通过mysql的逻辑运算符and连接
表达式一为: 2
表达式二为：unit_id = 14 （select unit_id = 14 from spoken where id = 284989;）
表达式三为：article_id = 47409 （select article_id = 47409 from spoken where id = 284989;）
由于当时unit_id = 55,article_id=55555
表达一的值为2
表达式二值为0
表达式三的值为0
所以select 2 and (unit_id = 14) and (article_id = 47409) from spoken where id = 284989;
的值为2 and 0 and 0 即为。
即执行语句的结果等价于update spoken set book_id = 0 where id = 284989;
Mysql的逻辑运算
http://www.cnblogs.com/pzk7788/p/6891299.html
逻辑与 ( AND 或 && )
(1) 当所有操作数均为非零值、并且不为 NULL 时，所得值为 1
(2) 当一个或多个操作数为 0 时，所得值为 0
(3) 其余情况所得值为 NULL
mysql> SELECT 1 AND -1, 1 && 0, 0 AND NULL, 1 && NULL ;
+----------+--------+------------+-----------+
| 1 AND -1
| 1 && 0
| 0 AND NULL | 1 && NULL |
+----------+--------+------------+-----------+
| 1 | 0 | 0
| NULL |
+----------+--------+------------+-----------+
二、同理可得语句三
2 and unit_id = 14 and article_id = 47409
相当于将book_id的值更新为下面语句的值
select 2 and (unit_id = 14) and (article_id = 47409) from spoken where id = 284989;
该语句由三个表达式通过mysql的逻辑运算符and连接
表达式一为: 2
表达式二为：unit_id = 14 （select unit_id = 14 from spoken where id = 284989;）
表达式三为：article_id = 47409 （select article_id = 47409 from spoken where id = 284989;）
由于当时unit_id = 14,article_id=47409
表达一的值为2
表达式二值为1
表达式三的值为1
所以select 2 and (unit_id = 14) and (article_id = 47409) from spoken where id = 284989;
的值为2 and 1 and 1 即为1。
即执行语句的结果等价于update spoken set book_id = 1 where id = 284989;
额外的问题：
Mysql如果对mysql的数值型如int做匹配时，unit_id字段和14做匹配时
如下三个语句都匹配到结果
select id,book_id,unit_id,article_id from spoken where unit_id=14;
select id,book_id,unit_id,article_id from spoken where unit_id='14';
select id,book_id,unit_id,article_id from spoken where unit_id='14aaa';
（字符串转数值会截取第一个非数字前面的数字）
mysql> select id,book_id,unit_id,article_id from spoken where unit_id=14;
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 0 | 14 | 47409 |
+--------+---------+---------+------------+
1 row in set (0.00 sec)
mysql> select id,book_id,unit_id,article_id from spoken where unit_id='14';
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 0 | 14 | 47409 |
+--------+---------+---------+------------+
1 row in set (0.00 sec)
mysql> select id,book_id,unit_id,article_id from spoken where unit_id='14aaa';
+--------+---------+---------+------------+
| id | book_id | unit_id | article_id |
+--------+---------+---------+------------+
| 284989 | 0 | 14 | 47409 |
+--------+---------+---------+------------+
1 row in set, 1 warning (0.00 sec)
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