如果另一个表中的值不可用,如何连接两个表并返回 null 值?
我试图加入我发现的很多例子,但是我很难得到希望。谢谢!
答案 0 :(得分:0)
尝试 LEFT OUTER JOIN
SELECT *
FROM Table1 t -- Specify the table whose value you need to display even when no match is found
LEFT OUTER JOIN Table2 t2
ON t.id=t2.t_id
答案 1 :(得分:0)
使用 LEFT JOIN :
SELECT
VA.COL_PERSONNEL_NUMBER,
VA.COL_CLOCK_DATE,
VA.P10,
VA.P20,
VR.NAME,
VR.UNIT
FROM VIEW_ABSEN VA
LEFT JOIN VIEW_REPORT VR ON VA.COL_PERSONNEL_NUMBER=VR.ID
AND VR.DATE=VA.COL_CLOCK_DATE
WHERE VA.COL_PERSONNEL_NUMBER LIKE '%521663%'
AND VA.COL_CLOCK_DATE BETWEEN '2016-08-01' AND '2016-08-05'