为此,将ORDER BY与LIMIT一起使用。让我们首先创建一个表,其中有一个包含用户ID,登录时间和名称的列-
mysql> create table DemoTable1911 ( UserId int, UserLoggedInTime time, UserName varchar(20) );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable1911 values(100,'7:32:00','Chris'); mysql> insert into DemoTable1911 values(101,'5:00:00','David'); mysql> insert into DemoTable1911 values(102,'6:10:20','Mike'); mysql> insert into DemoTable1911 values(103,'3:55:00','Carol');
使用select语句显示表中的所有记录-
mysql> select * from DemoTable1911;
这将产生以下输出-
+--------+------------------+----------+ | UserId | UserLoggedInTime | UserName | +--------+------------------+----------+ | 100 | 07:32:00 | Chris | | 101 | 05:00:00 | David | | 102 | 06:10:20 | Mike | | 103 | 03:55:00 | Carol | +--------+------------------+----------+ 4 rows in set (0.00 sec)
这是用于更新特定用户“ Carol”的登录时间的查询-
mysql> update DemoTable1911 set UserLoggedInTime='12:30:45' where UserName='Carol' order by UserId DESC Limit 1; Rows matched: 1 Changed: 1 Warnings: 0
让我们再次检查表记录-
mysql> select * from DemoTable1911;
这将产生以下输出-
+--------+------------------+----------+ | UserId | UserLoggedInTime | UserName | +--------+------------------+----------+ | 100 | 07:32:00 | Chris | | 101 | 05:00:00 | David | | 102 | 06:10:20 | Mike | | 103 | 12:30:45 | Carol | +--------+------------------+----------+ 4 rows in set (0.00 sec)