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在MySQL中选择WHERE IN null吗？

2024-04-20 12:30:04 424

以下是语法-

select
yourColumnName1,
yourColumnName2,
yourColumnName3,
.
.
.
N
from yourTableName
where yourValue in(yourColumnName1,yourColumnName2) or yourColumnName1 is NULL;

让我们创建一个表-

mysql> create table demo60
−> (
−> id int not null auto_increment primary key,
−> first_name varchar(20),
−> last_name varchar(20)
−> )
−> ;

借助insert命令将一些记录插入表中-

mysql> insert into demo60(first_name,last_name) values('John','Smith');

mysql> insert into demo60(first_name,last_name) values('John','Doe');

mysql> insert into demo60(first_name,last_name) values(null,'Brown');

mysql> insert into demo60(first_name,last_name) values('David','Miller');

mysql> insert into demo60(first_name,last_name) values('David','Smith');

mysql> insert into demo60(first_name,last_name) values('Chris','Brown');

使用select语句显示表中的记录-

mysql> select *from demo60;

这将产生以下输出-

+----+------------+-----------+
| id | first_name | last_name |
+----+------------+-----------+
|  1 | John       | Smith     |
|  2 | John       | Doe       |
|  3 | NULL       | Brown     |
|  4 | David      | Miller    |
|  5 | David      | Smith     |
|  6 | Chris      | Brown     |
+----+------------+-----------+
6 rows in set (0.00 sec)

以下是选择NULL的查询-

Mysql> select
−> id,
−> first_name,
−> last_name
−> from demo60
−> where 'John' in(first_name,last_name) or first_name is NULL;

这将产生以下输出-

+----+------------+-----------+
| id | first_name | last_name |
+----+------------+-----------+
| 1  | John       | Smith     |
| 2  | John       | Doe       |
| 3  | NULL       | Brown     |
+----+------------+-----------+
3 rows in set (0.00 sec)

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在MySQL中选择WHERE IN null吗？

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