MySQL 如何声明 datetime 变量?
mysqlmysqli database
要声明 datetime 变量，您需要使用 SET 命令使用用户定义变量。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) -> ); Query OK, 0 rows affected (0.78 sec)
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');
Query OK, 1 row affected (0.53 sec)
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('Sam','2012-04-25 15:30:25');
Query OK, 1 row affected (0.18 sec)
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('Larry','2013-10-04 16:40:30');
Query OK, 1 row affected (0.10 sec)
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('Bob','2014-05-15 10:30:25');
Query OK, 1 row affected (0.33 sec)
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('Mike','2017-08-13 11:30:25');
Query OK, 1 row affected (0.08 sec)
mysql> insert into datetimeVariables(Name,ArrivalDatetime) values('David','2018-04-25 09:30:25');
Query OK, 1 row affected (0.20 sec)
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'; Query OK, 0 rows affected (0.00 sec)
以下是在选择查询中使用变量。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)
