在MySQL中实现GREATEST()并更新表？
让我们首先创建一个表-
mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Number int );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable(Number) values(10); mysql> insert into DemoTable(Number) values(50); mysql> insert into DemoTable(Number) values(100); mysql> insert into DemoTable(Number) values(190);
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-
+----+--------+ | Id | Number | +----+--------+ | 1 | 10 | | 2 | 50 | | 3 | 100 | | 4 | 190 | +----+--------+ 4 rows in set (0.00 sec)
以下是要greatest()在MySQL中更新的查询-
mysql> update DemoTable set Number=GREATEST(200,Number) WHERE Id=3; Rows matched: 1 Changed: 1 Warnings: 0
让我们再次显示表记录-
mysql> select *from DemoTable;
这将产生以下输出-
+----+--------+ | Id | Number | +----+--------+ | 1 | 10 | | 2 | 50 | | 3 | 200 | | 4 | 190 | +----+--------+ 4 rows in set (0.00 sec)