Question

我有一个小的存储过程，它正在拉入记录。目前该表中有2条记录。其中一个的值为A.[managerApproval]而另一个则没有。由于连接，如果列没有值，则整个记录不会显示而不仅仅是空值。

无论其加入的列是否具有值，仍然显示数据的好方法是什么？

SELECT A.[id],
       A.[empID],
       A.[firstName],
       A.[lastName],
       A.[emailAddress],
       B.[FirstName] + ' ' +B.[LastName] + ' (' +B.[ntid]+ ')' as managerApproval
FROM   tuitionSubmissions as A
JOIN empTable AS B
ON B.[empID] = A.[managerApproval]
FOR    XML PATH ('data'), TYPE, ELEMENTS, ROOT ('root');

Answer 1

使用LEFT OUTER JOIN - 如果第二个表格中存在值，它会将值加入表格，否则它会返回NULL您SELECT中的任何值第二桌。

SELECT A.[id],
       A.[empID],
       A.[firstName],
       A.[lastName],
       A.[emailAddress],
       B.[FirstName] + ' ' +B.[LastName] + ' (' +B.[ntid]+ ')' as managerApproval
FROM   tuitionSubmissions as A
LEFT OUTER JOIN empTable AS B
ON B.[empID] = A.[managerApproval]
FOR    XML PATH ('data'), TYPE, ELEMENTS, ROOT ('root');

对于这些记录，managerApproval将为NULL

Answer 2

好像你需要一个左连接：

  SELECT A.[id],
       A.[empID],
       A.[firstName],
       A.[lastName],
       A.[emailAddress],
       B.[FirstName] + ' ' +B.[LastName] + ' (' +B.[ntid]+ ')' as managerApproval
    FROM   tuitionSubmissions as A
    Left JOIN empTable AS B
    ON B.[empID] = A.[managerApproval]
   FOR    XML PATH ('data'), TYPE, ELEMENTS, ROOT ('root');

TSQL连接可能为空值

2 个答案: