mySQL查詢得到的記錄不匹配

Question

我有一個sql查詢，我想添加另一個條件，但我似乎無法得到它的工作。該查詢很簡單：

SELECT DISTINCT monthly_returns.company_id 
     FROM monthly_returns, paidreturns 
     WHERE monthly_returns.company_id = paidreturns.company_id 
     AND paidreturns.month = '$cdate' 
     AND paidreturns.paid =0 

但是我想從那些尚未在paidreturns對於給定日期的所有記錄monthly_returns得到記錄也。我知道這將是這樣的

SELECT * 
FROM monthly_returns 
WHERE monthly_returns NOT IN (SELECT * FROM paidreturns WHERE paidreturns.month = '$cdate') 

paidreturns.paid = 0時，由票據尚未支付，但如果同樣存在於paidreturns該日期，然後該法案也沒有支付任何記錄。

架構

paidreturns表

-id

-company_id

-paid

個月的

-total

monthly_returns表

-id

-company_id

-wage_totals

個月的

Answer 1

試試這個：

SELECT 
    DISTINCT monthly_returns.company_id 
FROM 
    monthly_returns 
LEFT JOIN 
    paidreturns 
    ON monthly_returns.company_id = paidreturns.company_id 
     AND monthly_returns.month = paidreturns.month 
WHERE 
    monthly_returns.month = '$cdate' 
    AND 
     (
     paidreturns.paid = 0 
     OR 
     paidreturns.company_id IS NULL 
     ); 

使用LEFT JOIN，您可以找到monthly_returns中的所有記錄，無論它們是否與paidreturns中的條目匹配。

然後，通過將paidreturns.company_id IS NULL添加到WHERE子句中，可以在查詢中包含那些不匹配的條目。

Answer 2

select company_id 
from 
(
(

SELECT DISTINCT monthly_returns.company_id 
    FROM monthly_returns, paidreturns 
    WHERE monthly_returns.company_id = paidreturns.company_id 
    AND paidreturns.month = '$cdate' 
    AND paidreturns.paid =0 
) 
union 
(


SELECT company_id 
FROM monthly_returns 
WHERE monthly_returns NOT IN (SELECT * FROM paidreturns WHERE paidreturns.month = '$cdate' 
) 
) as x