SQL Join 返回空集

Question

I'm having problems with my SQL Join. I want to join two tables on a specific ID number and during a specific time frame, but I just keep getting an empty set returned. What I want to get is a match between both tables on the ID numbers, and also filter it by time, also called "Term". Term is on the ProcInfo table I believe. Any ideas on what I'm doing wrong?

    SELECT*
    FROM tblPernfo INNER JOIN tblProcInfo ON tblProcInfo.eID=tblPernfo.eID
    WHERE Term In ('1st Sum 2010')
    ORDER BY Term;

Answer 1

First

SELECT (specify columns here)     
FROM tblPernfo 
INNER JOIN tblProcInfo ON tblProcInfo.eID=tblPernfo.eID     
WHERE Term In ('1st Sum 2010')     
ORDER BY Term; 

it is very poor practice to use select *. It causes performance problems.

Why are you using IN? = should work.

Now to get to why no records are returned. This is a simple dataset, so there are only a coupl eof possibilities. First is that there are no records in tblProcInfo that match to records in tblPernfo. You can confirm or exclude this possibility by running the statement without the where clause.

SELECT (specify columns here)     
FROM tblPernfo 
INNER JOIN tblProcInfo ON tblProcInfo.eID=tblPernfo.eID   

If it returns records, the where clause is the issue, if it does not the join ins the issue. Next run this ( or substitute tblProcInfo idf that is the table that contains the Term column:

SELECT (specify columns here)     
FROM tblPernfo   
WHERE Term In ('1st Sum 2010')     

If that returns data and the first query returned records then the only possibility left is that there are no records in the second table that match the first table for this specific value.