编写单个MySQL查询以排除记录并显示NULL值
若要检查为空的记录，请使用ISNULL。但是，要排除任何记录，请使用NOTIN子句。在同一查询中使用它们两者。
让我们首先创建一个表-
mysql> create table DemoTable793 ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentName varchar(100) );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable793(StudentName) values('Adam');
mysql> insert into DemoTable793(StudentName) values('Bob');
mysql> insert into DemoTable793(StudentName) values(null);
mysql> insert into DemoTable793(StudentName) values('Chris');
mysql> insert into DemoTable793(StudentName) values('Robert');使用select语句显示表中的所有记录-
mysql> select *from DemoTable793;
这将产生以下输出-
+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | 1 | Adam | | 2 | Bob | | 3 | NULL | | 4 | Chris | | 5 | Robert | +-----------+-------------+ 5 rows in set (0.00 sec)
以下是查询以排除记录并显示NULL值-
mysql> select *from DemoTable793 where StudentName NOT IN('Chris') OR StudentName IS NULL;这将产生以下输出-
+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | 1 | Adam | | 2 | Bob | | 3 | NULL | | 5 | Robert | +-----------+-------------+ 4 rows in set (0.00 sec)