mysql - SQL中如何比较多行的值

Question

我有一个如下所示的源表..

Name    Subject Marks   Year

A   Science 88  2015
A   Social  75  2015
A   Social  75  2015
A   Maths   22  2015
B   Social  75  2015
B   Maths   50  2014
C   Science 88  2015
C   Social  75  2014
D   Science 88  2015
D   Social  75  2015
A   Social  75  2015
B   Maths   50  2014

我有如下要求，如果任何学生同时满足以下要求，那么他应该在另一个表 B 中被授予受尊重的要求集名称

Set1

Social  75  2015
Science 88  2015

Set2

Social  75  2015
Maths   50  2014

B表的预期输出如下

Name    Status
A   Set1
B   Set2
C   None
D   Set1

Answer 1

试试这个:

SELECT NAME,
       CASE WHEN SUM(SCIENCE) + SUM(SOCIAL) = 2 THEN 'GOOD' ELSE 'BAD' END AS Status
  FROM (SELECT NAME,
               CASE
                  WHEN SUBJECT = 'Science' AND MARKS = 88 AND YEAR = 2015
                  THEN 1 ELSE 0
               END
                  AS SCIENCE,
               CASE
                  WHEN SUBJECT = 'Social' AND MARKS = 75 AND YEAR = 2015
                  THEN  1 ELSE 0
               END
                  AS SOCIAL
          FROM A) group by Name;

SQLFiddle

[编辑] 如果您要添加一些规则，请在子查询中添加一个案例，并更新最重要的案例:

    SELECT NAME,
       CASE WHEN MAX(SCIENCE) + MAX(SOCIAL) = 2 THEN 'Set1' 
       WHEN MAX(SOCIAL) + MAX(MATHS) =2 THEN 'Set2'
       ELSE 'None'END AS Status
  FROM (SELECT NAME,
               CASE
                  WHEN SUBJECT = 'Science' AND MARKS = 88 AND YEAR = 2015
                  THEN 1 ELSE 0
               END
                  AS SCIENCE,
               CASE
                  WHEN SUBJECT = 'Social' AND MARKS = 75 AND YEAR = 2015
                  THEN  1 ELSE 0
               END
                  AS SOCIAL,
              CASE
                  WHEN SUBJECT = 'Maths' AND MARKS = 50 AND YEAR = 2014
                  THEN  1 ELSE 0
               END AS MATHS
          FROM A)x group by Name;

参见 SQLFiddle