T-SQL：测试条件如果匹配其他表，否则包括不测试

Question

这是我尝试做的事情，但我无法正确理解语法：

SELECT 
    myKey1, myDate1
FROM 
    myTable1, 
    (SELECT myKey2, myDate2 FROM myTable2) as myDatesQuery
WHERE
    -- myTable1.myKey1 = myDatesQuery.myKey2 AND myTable1. myDate1 < myDatesQuery. myDate2
    -- OR myTable1.myKey1 not found in myDatesQuery

因此，如果myKey1在myDatesQuery中不存在，那么请包含它。如果myKey1 = myKey2只包括myDate1在myDate2之前。

非常感谢

Answer 1

尝试：

Select myTable1.myKey1, myTable1.myDate1
    FROM 
(SELECT myKey2, myDate2 FROM myTable2) as myDatesQuery
left outer join myTable1 
        on myTable1.myKey1 = myDatesQuery.myKey2
        where myTable1.myKey1 is null or myTable1.myDate1< myDatesQuery.MyDate2