SQL查询以查找表中列值多次出现的计数？

Posted 2023-03-31

【中文标题】SQL查询以查找表中列值多次出现的计数？

【英文标题】：SQL query to find count of multiple occurrences of column values from a table?

【发布时间】：2016-03-01 06:42:23

【问题描述】：

我的 SQL 查询遇到问题：

场景：我需要计算教师、主题和讲座日期相同的讲座时间段的多次出现次数。请参阅下面的所需输出部分和 SQL 查询。请告诉我可以对现有查询进行哪些更改。

表：“SCHOOL_RECORDS”

FACULTY_NAME   SUBJECT   LECTURE_DATE   LECTURE_TIME_SLOT
----------------------------------------------------------
Alex           Biology   10/01/2015     0900 - 1200
Alex           Biology   10/01/2015     0900 - 1200
Alex           Biology   10/01/2015     0900 - 1200
Lisa           Chemistry 10/01/2015     0900 - 1200
Lisa           Chemistry 10/01/2015     1700 - 2200
Lisa           Chemistry 10/01/2015     1700 - 2200
Lisa           Chemistry 11/01/2015     0900 - 1200

期望的输出：

FACULTY_NAME   SUBJECT   LECTURE_DATE   LECTURE_TIME_SLOT Count_Of_TimeSlots
----------------------------------------------------------------------------
Alex           Biology   10/01/2015     0900 - 1200       3
Lisa           Chemistry 10/01/2015     0900 - 1200       1
Lisa           Chemistry 10/01/2015     1700 - 2200       2
Lisa           Chemistry 11/01/2015     0900 - 1200       1

当前 SQL 查询：

Select a.FACULTY_NAME, 
       a.SUBJECT, 
       a.LECTURE_DATE, 
       a.LECTURE_TIME_SLOT, 
       b.Count_Of_TimeSlots

from SCHOOL_RECORDS a
inner join(
           select FACULTY_NAME, SUBJECT, LECTURE_DATE, LECTURE_TIME_SLOT,       
           count(LECTURE_TIME_SLOT) as Count_Of_TimeSlots 
           from SCHOOL_RECORDS 
           group by LECTURE_TIME_SLOT
          ) b 
on a.FACULTY_NAME = b.FACULTY_NAME and a.SUBJECT = b.SUBJECT and      
a.LECTURE_DATE = b.LECTURE_DATE and a.LECTURE_TIME_SLOT =   
b.LECTURE_TIME_SLOT;

提前致谢！

【参考方案1】：

试试这个..

 select FACULTY_NAME, SUBJECT, LECTURE_DATE, LECTURE_TIME_SLOT,       
       count(LECTURE_TIME_SLOT) as Count_Of_TimeSlots 
       from SCHOOL_RECORDS 
       group by FACULTY_NAME, SUBJECT, LECTURE_DATE,LECTURE_TIME_SLOT

【讨论】：

您需要在 GROUP BY 中使用 LECTURE_TIME_SLOT

哎呀..编辑查询...谢谢@Squirrel

【参考方案2】：

SELECT FACULTY_NAME, SUBJECT, LECTURE_DATE, LECTURE_TIME_SLOT, 
       COUNT(*) AS Count_Of_TimeSlots
FROM   SCHOOL_RECORDS
GROUP BY FACULTY_NAME, SUBJECT, LECTURE_DATE, LECTURE_TIME_SLOT