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编写单个MySQL查询以从相应行返回ID，该值是NOT NULL值

2024-04-24 16:20:02 373

让我们首先创建一个表-

mysql> create table DemoTable
(
   StudentId int,
   StudentName varchar(100)
);

使用插入命令在表中插入一些记录-

mysql> insert into DemoTable values(NULL,'Chris');
mysql> insert into DemoTable values(NULL,'Robert');
mysql> insert into DemoTable values(101,'David');
mysql> insert into DemoTable values(102,'Mike');
mysql> insert into DemoTable values(103,'Sam');

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-

+-----------+-------------+
| StudentId | StudentName |
+-----------+-------------+
|      NULL | Chris       |
|      NULL | Robert      |
|       101 | David       |
|       102 | Mike        |
|       103 | Sam         |
+-----------+-------------+
5 rows in set (0.00 sec)

以下是从相应行返回ID的查询，该值是NOTNULL值-

mysql> select StudentId from DemoTable where StudentName='David' and StudentId IS NOT NULL;

这将产生以下输出-

+-----------+
| StudentId |
+-----------+
|       101 |
+-----------+
1 row in set (0.00 sec)

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编写单个MySQL查询以从相应行返回ID，该值是NOT NULL值

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