使用不同的WHERE子句重構類似的子查詢

Question

我已經繼承了絕望需要重構的SQL查詢。查詢（6頁長）看起來是這樣的：

SELECT (count(*) from tab1, tab2, tab3 where tab1.value1 is not null 
and tab2.tab3id = tab3.id and tab3.value4 in (1,2,3) and tab3.value3 = 15 and tab2.value2 = 10 [...]) as RESULT1, 
SELECT (sum(tab3.value5) from [EXACT SAME QUERY AS ABOVE]) AS RESULT1_SUM 
SELECT (count(*) from tab1, tab2, tab3 where tab1.value1 is not null 
and tab2.tab3id = tab3.id and tab3.value4 in (1,2,3) and tab3.value3 = 15 and tab2.value2 = 27 [...]) as RESULT2, 
...[AD NAUSEAM for several more columns] 
UNION 
SELECT [same as first query, but now tab1.value1 is NULL] 
...[now sum()] 
FROM DUAL [of course!] 

這種混亂的最終結果是一個2行/ 16列結果，其中行由tab1.value1是否處於零不同（主要是複製和粘貼）子查詢，並且列的不同之處在於子查詢的WHERE子句的其他值中的小的任意變化。

   RESULT1 RESULT1_SUM RESULT2 RESULT2_SUM ... 
IS_NOT_NULL  300  120000  90   80000 
IS_NULL   70  90000  54   95000 

我必須複製這個相同的輸出。我的第一本能是將子查詢的常見元素放入WITH子句中。但我堅持如何獲得複製的「WHERE子句 - >不同的命名列」元素的微小變化，而不必爲每列使用單獨的子查詢。

我應該把它吸收並將子查詢轉儲到全局臨時表中還是有更好的方法？

Answer 1

如果列之間的主要區別是tab2.value2，那麼你可以寫由兩個階段的查詢：通過tab2.value2

外

1. 內查詢選擇相關的數據和分組它查詢分配結果到列

因此，對於您的查詢的前半部分，它可能會升ook是這樣的：

select 
    sum(case when val = 10 then cnt end) as RESULT1, 
    sum(case when val = 10 then sm end) as RESULT1_SUM, 
    sum(case when val = 15 then cnt end) as RESULT2, 
    sum(case when val = 15 then sm end) as RESULT2_SUM, 
    ... 
from (
    select tab2.value2 as val, count(*) as cnt, sum(tab3.value5) as sm 
    from tab1, tab2, tab3 
    where tab1.value1 is not null 
    and tab2.tab3id = tab3.id 
    and tab3.value4 in (1,2,3) 
    and tab3.value3 = 15 
    group by tab2.value2 
)