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MySQL如何声明一个datetime变量？

2024-05-14 16:51:05 525

要声明日期时间变量，您需要使用SET命令使用用户定义的变量。语法如下-

SET @anyVariableName=’yourdatetimeValue’;

为了理解上述语法，让我们创建一个表。创建表的查询如下-

mysql> create table datetimeVariables
   -> (
   -> Id int NOT NULL AUTO_INCREMENT,
   -> Name varchar(10),
   -> ArrivalDatetime datetime,
   -> PRIMARY KEY(Id)
   -> );

使用insert命令在表中插入一些记录。插入记录的查询如下-

mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('John','2011-01-31 13:45:20');
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('Sam','2012-04-25 15:30:25');
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('Larry','2013-10-04 16:40:30');
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('Bob','2014-05-15 10:30:25');
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('Mike','2017-08-13 11:30:25');
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('David','2018-04-25 09:30:25');

使用select语句显示表中的所有记录。查询如下-

mysql> select *from datetimeVariables;

以下是输出-

+----+-------+---------------------+
| Id | Name  | ArrivalDatetime     |
+----+-------+---------------------+
|  1 | John  | 2011-01-31 13:45:20 |
|  2 | Sam   | 2012-04-25 15:30:25 |
|  3 | Larry | 2013-10-04 16:40:30 |
|  4 | Bob   | 2014-05-15 10:30:25 |
|  5 | Mike  | 2017-08-13 11:30:25 |
|  6 | David | 2018-04-25 09:30:25 |
+----+-------+---------------------+
6 rows in set (0.00 sec)

以下是使用SET命令声明datetime变量的查询。查询如下-

mysql> set @greaterThan2011Datetime='2012-04-25 15:30:25';

以下是选择查询中变量的使用。查询如下-

mysql> select *from datetimeVariables
   -> where ArrivalDatetime> = @greaterThan2011Datetime;

以下是输出-

+----+-------+---------------------+
| Id | Name  | ArrivalDatetime     |
+----+-------+---------------------+
|  2 | Sam   | 2012-04-25 15:30:25 |
|  3 | Larry | 2013-10-04 16:40:30 |
|  4 | Bob   | 2014-05-15 10:30:25 |
|  5 | Mike  | 2017-08-13 11:30:25 |
|  6 | David | 2018-04-25 09:30:25 |
+----+-------+---------------------+
5 rows in set (0.00 sec)

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MySQL如何声明一个datetime变量？

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