Question

以下查询完美运行，并根据条件

插入行

INSERT INTO (t1.userid,t1.name,t1.email,t1.phone) SELECT 
t2.userid,t2.name,t2.email,t2.phone FROM t2 where t2.name!='';

但是，下面的查询插入0行，也不会抛出任何错误。通过使用多个where条件，查询无法正常工作

INSERT INTO (t1.userid,t1.name,t1.email,t1.phone) SELECT 
t2.userid,t2.name,t2.email,t2.phone FROM t2 where (t2.name!='' AND t2.name!=0 AND
 t2.name!=NULL)

Answer 1

您正在错误地进行空比较并且您应该使用not null

这是一个例子

mysql> select * from test ;
+------+------+
| id   | val  |
+------+------+
|    1 | NULL |
|    2 |      |
|    3 | 0    |
|    4 | aa   |
|    5 | cc   |
+------+------+
5 rows in set (0.00 sec

mysql> select * from test where val != '' and val != '0' and val != null;
Empty set (0.00 sec)


mysql> select * from test where val != '' and val != '0' and val is not null;
+------+------+
| id   | val  |
+------+------+
|    4 | aa   |
|    5 | cc   |
+------+------+
2 rows in set (0.00 sec)


mysql> select null != null ;
+--------------+
| null != null |
+--------------+
|         NULL |
+--------------+
1 row in set (0.00 sec)

mysql> select null is not null ;
+------------------+
| null is not null |
+------------------+
|                0 |
+------------------+
1 row in set (0.00 sec)

mysql> select null is  null ;
+---------------+
| null is  null |
+---------------+
|             1 |
+---------------+
1 row in set (0.00 sec)

所以在你的情况下，它将是

INSERT INTO (t1.userid,t1.name,t1.email,t1.phone) 
SELECT 
 t2.userid,t2.name,t2.email,t2.phone FROM t2 where (
 t2.name!='' 
 AND t2.name!='0' 
 AND t2.name is not NULL
)

Answer 2

要在mysql中检查NULL，请使用IS NULL关键字和IS NOT NULL

所以你的条件是：=

where (t2.name!='' AND t2.name!=0 AND
 t2.name IS NOT NULL);

在INERT INTO语句mysql中使用多个where子句

2 个答案: