SQL服务器的数量比多列

Question

我有这个表：

+-----------+--------+ 
| FILE CODE | STATES | 
+-----------+--------+ 
| TEST 1 | CA  | 
| TEST 2 | CA  | 
| TEST 1 | CA  | 
| TEST 2 | CA  | 
| TEST 3 | CA  | 
| TEST 4 | CA  | 
| TEST 5 | CA  | 
| TEST 1 | AZ  | 
| TEST 1 | LI  | 
| TEST 4 | CA  | 
| TEST 4 | CA  | 
+-----------+--------+ 

这应该是输出 （请参阅图像下方的票，但对输出一些麻烦）

+----------+--------+---------+ 
| FILECODE | STATES | COUNTS | 
+----------+--------+---------+ 
| TEST 1 | CA |  2 | 
| TEST 1 | AZ |  1 | 
| TEST 1 | LI |  1 | 
| TEST 2 | CA |  2 | 
| TEST 3 | CA |  1 | 
| TEST 4 | CA |  3 | 
| TEST 5 | CA |  1 | 
+----------+--------+---------+ 

代码：

SELECT 
    S.States, S.FIRST_MORTGAGE_PRIMARY_LOAN_TYPE, C.COUNTS 
FROM 
    Master_Files S 
INNER JOIN 
    (SELECT 
     States, FIRST_MORTGAGE_PRIMARY_LOAN_TYPE, 
     COUNT(FIRST_MORTGAGE_PRIMARY_LOAN_TYPE) as COUNTS 
    FROM 
     Master_Files 
    GROUP BY 
     States, FIRST_MORTGAGE_PRIMARY_LOAN_TYPE) C ON S.FIRST_MORTGAGE_PRIMARY_LOAN_TYPE = C.FIRST_MORTGAGE_PRIMARY_LOAN_TYPE 
                AND S.States = C.States 

Answer 1

没有理由在这里使用子查询一些练习。这个查询应该足够了：

SELECT states, 
     first_mortgage_primary_loan_type, 
     Count(first_mortgage_primary_loan_type) AS COUNTS 
FROM master_files 
GROUP BY states, first_mortgage_primary_loan_type 

Answer 2

只给你一个提示：:)

SELECT FILECODE, STATES, COUNT(*) AS COUNT 
FROM Table_Name 
GROUP BY FILECODE, STATES 

正如评论所说，这是一个基本的GROUP BY问题。 我劝你做出关于AGGREGATE FUNCTIONS（AVG，MAX，MIN，COUNT等）和GROUP BY声明