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MySQL查询只能一起显示空值和NULL值？

2024-04-24 00:30:05 344

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)

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MySQL查询只能一起显示空值和NULL值？

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