使用单个MySQL查询计算零，NULL和不同的值（零和NULL除外）
让我们首先创建一个表-
mysql> create table DemoTable( Value int );
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable values(10); mysql> insert into DemoTable values(NULL); mysql> insert into DemoTable values(10); mysql> insert into DemoTable values(0); mysql> insert into DemoTable values(20); mysql> insert into DemoTable values(10); mysql> insert into DemoTable values(0); mysql> insert into DemoTable values(NULL);
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-
+-------+ | Value | +-------+ | 10 | | NULL | | 10 | | 0 | | 20 | | 10 | | 0 | | NULL | +-------+ 8 rows in set (0.00 sec)
以下是对除null和0以外的所有值进行分组的查询-
mysql> select sum(Value is null) as NumberOfNull, sum(Value=0) as NumberOfZero, count(distinct Value > 0) as ValueExceptZeroAndNull from DemoTable;
这将产生以下输出-
+--------------+--------------+------------------------+ | NumberOfNull | NumberOfZero | ValueExceptZeroAndNull | +--------------+--------------+------------------------+ | 2 | 2 | 2 | +--------------+--------------+------------------------+ 1 row in set (0.00 sec)