選擇具有多個條件的父行

Question

我有這個查詢的大部分，直到一個新的條件出現，它讓我困惑。鑑於以下簡化表模式：

父表：

ID 
FName 
LName 

子表：

[Index] 
ParentID 
Active_Flag 
ExpirationDate 

我想要做的就是針對父行：

1. 有沒有孩子。
2. 有些孩子的Active_Flag爲1，但其有效日期爲空或NULL。
3. 的確是有孩子但沒有了Active_Flag設置爲1

下面的查詢提出了我的前兩個標準：

SELECT p.ID, p.LNAME, p.FNAME, 
    CASE 
     WHEN COUNT(ct.indx) = 0 THEN 'None' 
     WHEN ct.ExpirationDate is NULL or ct.ExpirationDate = '' THEN 'No expiration date' 
    END AS Issue 
FROM ParentTable AS p 
    LEFT JOIN ChildTable ct 
     ON p.ID = ct.ParentID 
GROUP BY p.ID, p.LNAME, p.FNAME, ct.[INDEX], ct.ExpirationDate 
HAVING (COUNT(ct.[INDEX]) = 0) OR (ct.ExpirationDate IS NULL OR ct.ExpirationDate = '') 
ORDER BY p.LNAME 

我不知道該如何解釋＃ 3。任何幫助表示讚賞。提前致謝。

Answer 1

你也可以做到這一點HAVING子句中：

SELECT p.ID, p.LNAME, p.FNAME, 
     (CASE WHEN COUNT(ct.indx) = 0 THEN 'None' 
      WHEN ct.ExpirationDate is NULL or ct.ExpirationDate = '' THEN 'No expiration date' 
      WHEN sum(case when ActiveFlag = 1 then 1 else 0 end) = 0 then 'No active children' 
     END) AS Issue 
FROM ParentTable p LEFT JOIN 
    ChildTable c 
    ON p.ID = ct.ParentID 
GROUP BY p.ID, p.LNAME, p.FNAME 
HAVING (COUNT(ct.[INDEX]) = 0) OR 
     (ct.ExpirationDate IS NULL OR ct.ExpirationDate = '') or 
     sum(case when ActiveFlag = 1 then 1 else 0 end) = 0 
ORDER BY p.LNAME 

的DISTINCT的SELECT是多餘的。你不需要聚合。

如果activeFlag確實是一個整數，則可以簡化不得不使用「sum（ActiveFlag）」。如果不是，那麼它應該是「='1'」而不是「= 1」。

Answer 2

您可以使用此聯合查詢..... 我不確定這個查詢....但它將幫助您解決prolem

select p.id,p.lname,p.fname from parents where (p.id not in (select pid from children)) 
    union 
    select p.id,p.lname,p.fname from parents p,children c inner join on c.pid=p.id where c.active_flag=1 and c.expiration_date is null or c.expiration_date='' 
    union 
    select p.id,p.lname,p.fname from parents p inner join on c.pid=p.id where c.active_flag<>1; 

Answer 3

SELECT * 
FROM parenttable pt 
     -- condition 1: There should be no parents without children at all 
WHERE NOT EXISTS (
     SELECT * FROM childtable c1 
     WHERE c1.parent_id = pt.id 
     ) 
     -- condition 2: There should be no children with a flag but without a date 
OR EXISTS (
     SELECT * FROM childtable c2 
     WHERE c2.parent_id = pt.id 
     AND c2.active_flag = 1 AND c2.expire_date IS NULL 
     ) 
     -- condition 3: There should at least be a child with the active_flag 
OR NOT EXISTS (
     SELECT * FROM childtable c3 
     WHERE c3.parent_id = pt.id 
     AND c2.active_flag = 1 
     ) 
     ; 

-- Active flags for children c1 and c2 
-- c1 c2 (X= child doesn't exists) 
-----+-----+---+ 
-- X X  rule1+rule3  # no children at all 
-- 0 X  rule3   # only one child 
-- 1 X      # idem 
-- 0 0  rule 3   # two children 
-- 0 1 
-- 1 0 
-- 1 1 
-- 
-- , which means that rule3 implies rule1, and rule1 is redundant 
------------------------- 

SELECT * 
FROM parenttable pt 
     -- condition 1+3: There should at least be a child with the active_flag 
WHERE NOT EXISTS (
     SELECT * FROM childtable c1 
     WHERE c1.parent_id = pt.id 
     AND c1.active_flag = 1 
     ) 
     -- condition 2: There should be no children with a flag but without a date 
OR EXISTS (
     SELECT * FROM childtable c2 
     WHERE c2.parent_id = pt.id 
     AND c2.active_flag = 1 AND c2.expire_date IS NULL 
     ) 
     ;