MySQL查询只能一起显示空值和NULL值？
要检查NULL，请使用ISNULL。对于空值，您需要检查一个空字符串。现在，我们将看到一个示例。
让我们首先创建一个表-
mysql> create table DemoTable691( PlayerId int NOT NULL AUTO_INCREMENT PRIMARY KEY, PlayerName varchar(100), PlayerScore int );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable691(PlayerName,PlayerScore) values('Robert',56);
mysql> insert into DemoTable691(PlayerName,PlayerScore) values('David',89);
mysql> insert into DemoTable691(PlayerName,PlayerScore) values('',98);
mysql> insert into DemoTable691(PlayerName,PlayerScore) values(null,71);使用select语句显示表中的所有记录-
mysql> select *from DemoTable691;
这将产生以下输出-
+----------+------------+-------------+ | PlayerId | PlayerName | PlayerScore | +----------+------------+-------------+ | 1 | Robert | 56 | | 2 | David | 89 | | 3 | | 98 | | 4 | NULL | 71 | +----------+------------+-------------+ 4 rows in set (0.00 sec)
以下是MySQL查询，以一起显示空值和NULL值-
mysql> select *from DemoTable691 where PlayerName IS NULL OR PlayerName='';
这将产生以下输出-
+----------+------------+-------------+ | PlayerId | PlayerName | PlayerScore | +----------+------------+-------------+ | 3 | | 98 | | 4 | NULL | 71 | +----------+------------+-------------+ 2 rows in set (0.00 sec)