MySql多次計算同一列

Question

SELECT COUNT(w.invoiceId) AS '10 Days' FROM tbl_Invoice w
WHERE w.invoiceId NOT IN(
SELECT inv.invoiceId FROM tbl_InvoiceAllocation inv)
AND w.invoiceDate < DATE_SUB(curdate(), INTERVAL 10 DAY)

它工作正常，並返回日期超過10天的所有發票的計數。 我現在想要在同一查詢中返回超過20天和100天的發票的計數。 理想情況下，查詢將返回如下內容：

10 Days    20 Days    100 Days

350        280        90

Answer 1

使用指定的WHERE子句作為CASE語句將COUNT更改為SUM，其中true值為1，false值為0

就像是

SELECT  SUM( CASE WHEN w.invoiceDate < DATE_SUB(curdate(), INTERVAL 10 DAY) THEN 1 ELSE 0 END) AS '10 Days',
        SUM( CASE WHEN w.invoiceDate < DATE_SUB(curdate(), INTERVAL 20 DAY) THEN 1 ELSE 0 END) AS '20 Days'
FROM    tbl_Invoice w 
WHERE   w.invoiceId NOT IN( 
                            SELECT  inv.invoiceId 
                            FROM    tbl_InvoiceAllocation inv) 
AND     w.invoiceDate < DATE_SUB(curdate(), INTERVAL 20 DAY)