对于用户定义的变量,我们在MySQL中使用@。以下是语法。在这里,@anyVariableName是我们的用户定义变量-
select yourColumnName into @anyVariableName from yourTableName where yourCondition;
让我们首先创建一个表-
create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(100) );
使用插入命令在表中插入一些记录-
insert into DemoTable(Name) values('Chris'); insert into DemoTable(Name) values('Robert'); insert into DemoTable(Name) values('David');
使用select语句显示表中的所有记录-
select *from DemoTable;
这将产生以下输出-
+----+--------+ | Id | Name | +----+--------+ | 1 | Chris | | 2 | Robert | | 3 | David | +----+--------+ 3 rows in set (0.00 sec)
以下是使用MySQL选择用户定义变量的查询-
select Name into @FirstName from DemoTable where Id=3;
让我们检查变量的值-
select @FirstName;
这将产生以下输出-
+------------+ | @FirstName | +------------+ | David | +------------+ 1 row in set (0.00 sec)