如何在MySQL中正确使用WITH ROLLUP？

使用WITH ROLLUP的语法如下-

select yourColumnName1,sum(yourColumnName2) from yourTableName
 group by yourColumnName1 with rollup;

让我们首先创建一个表-

mysql> create table DemoTable1622
    -> (
    -> EmployeeCountryName varchar(20),
    -> EmployeeSalary int
    -> );

使用插入命令在表中插入一些记录-

mysql> insert into DemoTable1622 values('US',4500);
mysql> insert into DemoTable1622 values('UK',1500);
mysql> insert into DemoTable1622 values('AUS',1700);
mysql> insert into DemoTable1622 values('UK',1900);
mysql> insert into DemoTable1622 values('US',3900);

使用select语句显示表中的所有记录-

mysql> select * from DemoTable1622;

这将产生以下输出-

+---------------------+----------------+
| EmployeeCountryName | EmployeeSalary |
+---------------------+----------------+
| US                  |           4500 |
| UK                  |           1500 |
| AUS                 |           1700 |
| UK                  |           1900 |
| US                  |           3900 |
+---------------------+----------------+
5 rows in set (0.00 sec)

这是在MySQL中正确使用WITH ROLLUP的查询-

mysql> select EmployeeCountryName,sum(EmployeeSalary) from DemoTable1622
    -> group by EmployeeCountryName with rollup;

这将产生以下输出-

+---------------------+---------------------+
| EmployeeCountryName | sum(EmployeeSalary) |
+---------------------+---------------------+
| AUS                 |                1700 |
| UK                  |                3400 |
| US                  |                8400 |
| NULL                |               13500 |
+---------------------+---------------------+
4 rows in set (0.02 sec)