mysql中如何查询varchar类型字段为空的纪录

设置条件为:
null,NULL
"",''
均告失败，就是查询不出来

惭愧~这问题貌似有些弱智

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对了，我用的管理工具是mysqladmin
不知道这有没有影响

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刚得知应该
is null

而不是用=

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空字符串为： =''

null值则为：  where field_name is (not) null 或 ifnull(field_name,'')=''

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SQL code:
SELECT * fromM TB WHERE 字段 IS NULL OR 字段='' OR LOWER(字段)=LOWER('NULL')

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select * from yourTable where col is null;

SQL code:
mysql> select * from t_asoliddream66;
+------+------+
| id | col |
+------+------+
| 1 | NULL |
| 2 | aaa |
| 3 | NULL |
| 4 | bbb |
+------+------+
4 rows in set (0.05 sec)

mysql> select * from t_asoliddream66 where col is null;
+------+------+
| id | col |
+------+------+
| 1 | NULL |
| 3 | NULL |
+------+------+
2 rows in set (0.08 sec)

mysql>