Question

我在获取正确数据时遇到问题......

我有两个表， tblbuilding和tbldata。

这是我的 tblbuilding ：

enter image description here

这是我的 tbldata ：

enter image description here

我的疑问：

我的fldWeek在这里是“第3周”：

SELECT tblbuilding.fldBldgName
      ,tblbuilding.fldNetname
      ,MAX(tbldata.fldDuration) AS fldDuration
      ,tbldata.fldWeek
      ,tbldata.fldYear
FROM tblbuilding AS tblbuilding_1 
    LEFT OUTER JOIN tbldata ON tblbuilding_1.fldBldgName = tbldata.fldBldgName 
    CROSS JOIN tblbuilding
WHERE (tblbuilding.fldNetname = 'LRT - 2') 
    AND (tbldata.fldWeek = 'Week 3' OR tbldata.fldWeek IS NULL)
    AND (tbldata.fldYear = '2013' OR tbldata.fldYear IS NULL)
GROUP BY tbldata.fldWeek
        ,tblbuilding.fldBldgName
        ,tblbuilding.fldNetname
        ,tbldata.fldYear
ORDER BY tblbuilding.fldBldgName

上述查询的结果是：

enter image description here

哪个是正确的......

但当我将fldWeek改为“第2周”时

结果是：

enter image description here

正确的结果应该是......“假设我在WEEK 2中只有两个NOT NULL”

enter image description here

...谢谢

Answer 1

我认为你不需要获得笛卡尔积。

仅使用LEFT JOIN尝试此操作。

SELECT  a.ID,
        a.fldBldgName,
        b.fldDuration,
        b.fldWeek,
        b.fldYear
FROM    tblBuilding a
        LEFT JOIN tblData b
            ON  a.fldBldgName = b.fldBldgName
                AND b.fldWeek = 'Week 3'
                AND b.fldYear = '2013'
WHERE   a.fldNetname = 'LRT - 2'

SQL QUERY：连接两个表

1 个答案: