在MySQL中为NULL或空值设置自定义值
让我们首先创建一个表-
mysql> create table DemoTable ( Value varchar(100) );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values('100');
mysql> insert into DemoTable values('');
mysql> insert into DemoTable values('200');
mysql> insert into DemoTable values(null);使用select语句显示表中的所有记录-
mysql> select *from DemoTable;
这将产生以下输出-
+-------+ | Value | +-------+ | 100 | | | | 200 | | NULL | +-------+ 4 rows in set (0.00 sec)
以下是为NULL或空值设置自定义值的查询-
mysql> select if(Value IS NULL or Value='','Garbage Value',Value) AS Result from DemoTable;
这将产生以下输出-
+---------------+ | Result | +---------------+ | 100 | | Garbage Value | | 200 | | Garbage Value | +---------------+ 4 rows in set (0.00 sec)