sql - SQL count() 帮助选择语句

Question

我正在使用这段代码：

  SELECT MACH_NO, 
         COUNT(MACH_NO) AS TOTAL_REPORTS
    FROM MAINTENANCE_LOG
GROUP BY MACH_NO;

...检索一些数据，这些数据给出：

MACH_NO  TOTAL_REPORTS
----------------------
1        4
5        2
8        1
7        1

如何仅在总报告大于三个的情况下检索？我试过：

WHERE TOTAL_REPORTS > 3 

...但它说

ORA-00904: "TOTAL_REPORTS": 标识符无效

Answer 1

由于您使用了 a GROUP BY，因此您应该使用HAVING而不是WHERE. 您还需要明确使用COUNT(MACH_NO)而不是您的别名TOTAL_REPORTS.

所以使用HAVING COUNT(MACH_NO) > 3，而不是WHERE TOTAL_REPORTS > 3。

SELECT MACH_NO, 
       COUNT(MACH_NO) AS TOTAL_REPORTS 
FROM MAINTENANCE_LOG 
GROUP BY MACH_NO
HAVING COUNT(MACH_NO) > 3;

Answer 2

使用HAVING CLAUSE

SELECT MACH_NO, COUNT(MACH_NO) AS TOTAL_REPORTS FROM MAINTENANCE_LOG GROUP BY MACH_NO HAVING TOTAL_REPORTS > 3;

Answer 3

SELECT MACH_NO, COUNT(MACH_NO) AS TOTAL_REPORTS 从 MAINTENANCE_LOG GROUP BY MACH_NO having count(mach_no) > 3

Answer 4

而不是 WHERE TOTAL_REPORTS > 3，尝试 WHERE COUNT(MACH_NO) > 3。