mySQL查询得到的记录不匹配

Question

我有一个sql查询，我想添加另一个条件，但我似乎无法得到它的工作。该查询很简单：

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 

但是我想从那些尚未在paidreturns对于给定日期的所有记录monthly_returns得到记录也。我知道这将是这样的

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

paidreturns.paid = 0时，由票据尚未支付，但如果同样存在于paidreturns该日期，然后该法案也没有支付任何记录。

架构

paidreturns表

-id

-company_id

-paid

个月的

-total

monthly_returns表

-id

-company_id

-wage_totals

个月的

Answer 1

试试这个：

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中的所有记录，无论它们是否与paidreturns中的条目匹配。

然后，通过将paidreturns.company_id IS NULL添加到WHERE子句中，可以在查询中包含那些不匹配的条目。

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