如何在MySQL中返回不同的值及其计数？
要仅返回不同的值，请使用GROUPBY子句。
让我们首先创建一个表-
mysql> create table DemoTable754 (ProductPrice int);
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable754 values(200); mysql> insert into DemoTable754 values(500); mysql> insert into DemoTable754 values(200); mysql> insert into DemoTable754 values(500); mysql> insert into DemoTable754 values(800); mysql> insert into DemoTable754 values(900); mysql> insert into DemoTable754 values(200); mysql> insert into DemoTable754 values(200); mysql> insert into DemoTable754 values(900);
使用select语句显示表中的所有记录-
mysql> select *from DemoTable754;
这将产生以下输出-
+--------------+ | ProductPrice | +--------------+ | 200 | | 500 | | 200 | | 500 | | 800 | | 900 | | 200 | | 200 | | 900 | +--------------+ 9 rows in set (0.00 sec)
以下是返回不同值及其计数的查询-
mysql> select ProductPrice,count(ProductPrice) from DemoTable754 group by ProductPrice;
这将产生以下输出-
+--------------+---------------------+ | ProductPrice | count(ProductPrice) | +--------------+---------------------+ | 200 | 4 | | 500 | 2 | | 800 | 1 | | 900 | 2 | +--------------+---------------------+ 4 rows in set (0.00 sec)