Question

以下SQL查询对我有用，但是当staffNo为空6次时（每个工作人员一次），它返回属性值。即使staffNo为null，也没有6次返回，我想返回属性所有者。

SELECT s.branchNo, s.staffNo, s.fName, s.lName, propertyNo, p.staffNo,
       o.fName, o.lName, o.ownerNo
  FROM staff s, propertyforrent p, privateowner o
 WHERE s.staffNo = p.staffNo AND o.ownerNo = p.ownerNo
    OR p.staffNo IS NULL     AND o.ownerNo = p.ownerNo
 ORDER BY s.branchNo, s.staffNo, propertyNo

结果

B003    SG14    David   Ford    PG16    SG14    Tony    Shaw    CO93
B003    SG14    David   Ford    PG4     NULL    Tina    Murphy  CO40
B003    SG37    Ann     Beech   PG21    SG37    Carol   Farrel  CO87
B003    SG37    Ann     Beech   PG36    SG37    Tony    Shaw    CO93
B003    SG37    Ann     Beech   PG4     NULL    Tina    Murphy  CO40
B003    SG5     Susan   Brand   PG4     NULL    Tina    Murphy  CO40
B005    SL21    John    White   PG4     NULL    Tina    Murphy  CO40
B005    SL41    Julie   Lee     PG4     NULL    Tina    Murphy  CO40
B005    SL41    Julie   Lee     PL94    SL41    Carol   Farrel  CO87
B007    SA9     Mary    Howe    PA14    SA9     Joe     Keogh   CO46
B007    SA9     Mary    Howe    PG4     NULL    Tina    Murphy  CO40

这是期望的结果

B003    SG14    David   Ford    PG16    SG14    Tony    Shaw    CO93
B003    SG14                    PG4     NULL    Tina    Murphy  CO40
B003    SG37    Ann     Beech   PG21    SG37    Carol   Farrel  CO87
B003    SG37    Ann     Beech   PG36    SG37    Tony    Shaw    CO93
B005    SL41    Julie   Lee     PL94    SL41    Carol   Farrel  CO87
B007    SA9     Mary    Howe    PA14    SA9     Joe     Keogh   CO46

提前致谢！

Answer 1

使用左连接可能会有所帮助

SELECT s.branchNo, s.staffNo, s.fName, s.lName, propertyNo, p.staffNo,
       o.fName, o.lName, o.ownerNo
  FROM privateowner o
  LEFT JOIN propertyforrent p ON o.ownerNo = p.ownerNo
  LEFT JOIN staff s ON s.staffNo = p.staffNo

 ORDER BY s.branchNo, s.staffNo, propertyNo

Answer 2

试试这个：

SELECT s.branchNo, s.staffNo, s.fName, s.lName, propertyNo, p.staffNo,
       o.fName, o.lName, o.ownerNo
  FROM staff AS s LEFT JOIN propertyforrent AS p
  ON s.staffNo = p.staffNo AND  p.staffNo IS NOT NULL
  LEFT JOIN privateowner AS o
 ORDER BY s.branchNo, s.staffNo, propertyNo;

Answer 3

希望这是正确的..

SELECT s.branchNo, s.staffNo, s.fName, s.lName, propertyNo, p.staffNo, o.fName, o.lName, o.ownerNo
FROM staff s 
join propertyforrent p on s.staffNo = p.staffNo
left join privateowner o on o.ownerNo = p.ownerNo
where p.staffNo is not null
ORDER BY s.branchNo, s.staffNo, propertyNo

大卫福特的空白栏是否故意？

值为IS NULL时删除SQL输出

3 个答案: