Question

Master_table Table_A

 ID   Problem    Date              ID   Problem     Date
101      123    01-02-1993        101       123   01-02-1993
101      124                      101       124
102      125                      102       125   07-02-1994
103      126    08-22-1999        103       126   08-22-1999
103      131                      103       131   08-09-1999

Table_B Table_C

 ID   Problem    Date              ID   Problem     Date
101      124                      101       124   
102      125    06-30-1994        102       125
103      126    08-22-1999        103       131   08-08-1999
103      131    08-09-1999        106       137   02-02-1987
106      137    01-02-1987        110       145   12-22-1995

我需要创建一个名为'final_table'的新表，以便Master_table中的所有观察都有一个日期。实现此目的的规则：来自Master_table的日期将用作Date存在的日期。否则，将使用Table_A，Table_B和Table_C中的最小日期。如果所有表中都缺少日期，则删除观察结果。

期望输出

ID   Problem    Date              
101      123    01-02-1993                            
102      125    06-30-1994                  
103      126    08-22-1999        
103      131    08-08-1999

我尝试了什么

SELECT ID, Problem, MIN(Date) as Date
FROM
(   SELECT ID, Problem, Date
    FROM Table_A
    UNION ALL
    SELECT ID, Problem, Date
    FROM Table_B
    UNION ALL
    SELECT ID, Problem, Date
    FROM Table_C
) as subQuery
Delete From table Where Date IS NULL

Answer 1

看来你需要以这种方式在3个表之间建立联盟

    select id, problem, data
    from Table_A
    where date is not null
    union 
    select id, problem, min(data)
    from Table_B
    group by id, problem
    where date is not null
    union
    select id, problem, min(data)
    from Table_B
    group by id, problem
    where date is not null

在SQL环境中基于四个不同的表组合日期

1 个答案: