需求:

求一段時間內各生產線前3名壞機的原因及壞機數.

step 1, 從將原始資料中抽取品質資料放於t96臨時表

create temp table t96 
on commit drop 
as 
select * from t96_pd_log where recseq between '791G0' and '792G0' and f96_op='PD-QC'  ;

select f96_line,f96_result, sum(f96_qty) as qty from t96 group by f96_line,f96_result order by f96_line,f96_result,qty desc
 

step2, 一條sql就能得到需求的結果, 其中用了with這個短句,類似於臨時表或子查詢的意思了,但如果用了with定義一個子集,在接著Select裡面可以多處引用.  下面SQL這個A子查詢每條生產線用不良數倒序排,並每記錄給一個行號 ...

with udc_qty_byline as 
(select f96_line,f96_result, sum(f96_qty) as qty from t96 group by f96_line,f96_result )
SELECT f96_line,f96_result,qty FROM 
(
    SELECT *, ROW_NUMBER() OVER (PARTITION BY 
             f96_line order by qty DESC) AS Row_ID FROM udc_qty_byline
) AS A
WHERE Row_ID <=3 ORDER BY f96_line
 

  Postgresql is powerful.