选择表中不具有可为空外键的另一行中的行

Question

I have the following database to use it in an Android 3.0 tablet application.

I want to select every Defect which it isn't on EReportDefect . As you can see EReportDefect.defectId could be null .

This select returns 0 rows. But there are defects which aren't on EReportDefect table.

SELECT 
  Defect.defectId,
  Defect.description
FROM 
  Defect 
WHERE 
   qapId = ? AND
   defectId NOT IN 
     (SELECT defectId FROM EReportDefect WHERE eReportId = ?);

What am I doing wrong?

Answer 1

You can join both table on column defectID using LEFT JOIN ,

SELECT  a.*
FROM    Defect a
        LEFT JOIN EReportDefect b
            ON a.defectID = b.defectID
WHERE   b.defectID IS NULL 

b.defectID will have NULL values if it has no match on a.defectID .

UPDATE 1

SELECT a.*
FROM    Defect a
        LEFT JOIN EReportDefect b
            ON a.defectID = b.defectID
WHERE  b.defectID IS NULL AND
        a.qapID = ? 
       -- AND b.ReportID = ?

Answer 2

This is how I make works:

SELECT
   Defect.defectId,
   Defect.description
FROM
   Defect
WHERE
   qapId = ? AND
   defectId NOT IN 
     (SELECT
        defectId
      FROM
        EReportDefect
      WHERE eReportId = ? AND defectId IS NOT NULL);

Answer 3

Maybe I am missing something but to me it seems if you remove "qapId = ? AND" and "WHERE eReportId = ?" it should just return results where there is not an entry in EReportDefect table

SELECT 
  Defect.defectId,
  Defect.description
FROM 
  Defect 
WHERE 
   defectId NOT IN 
     (SELECT defectId FROM EReportDefect);