Question

Here is a sample of my query:

SELECT ...
TRIM(eml.fxeml1) as "Email Address"
FROM pfship

LEFT JOIN mstfxem fax
ON fax.fxco=pfship.cshco AND fax.fxdiv=pfship.cshdiv AND fax.fxsold=pfship.cshsld
AND fax.fxtype='C' AND TRIM(fax.fxfax1) <> '' AND fax.fxdept LIKE '*F%'

LEFT JOIN mstfxem eml
ON eml.fxco=pfship.cshco AND eml.fxdiv=pfship.cshdiv AND eml.fxsold=pfship.cshsld
AND eml.fxtype='C' AND TRIM(eml.fxeml1) <> '' AND eml.fxdept LIKE '*E%'

WHERE ((pfship.cshco || '/' || pfship.cshdiv) = ?)
  AND (? = '*ALL' OR CAST(cshsld AS CHAR(15)) = ?) 
  AND ...
  ORDER BY TRIM(cshnme)

This query should return 9 records. When I remove:

LEFT JOIN mstfxem fax
ON fax.fxco=pfship.cshco AND fax.fxdiv=pfship.cshdiv AND fax.fxsold=pfship.cshsld
AND fax.fxtype='C' AND TRIM(fax.fxfax1) <> '' AND fax.fxdept LIKE '*F%'

LEFT JOIN mstfxem eml
ON eml.fxco=pfship.cshco AND eml.fxdiv=pfship.cshdiv AND eml.fxsold=pfship.cshsld
AND eml.fxtype='C' AND TRIM(eml.fxeml1) <> '' AND eml.fxdept LIKE '*E%'

I get 9 records, but with it I get 360 records. What is wrong with my join?

Thanks

I think the problem is that 1 person can have many emails or faxes, how do I group the results into 1 string per record so I end up with only 9 records?

Answer 1

Nothing is wrong with your join, you have a one to many relationship between the tables.

Depending on what you need there are several techniques. First is the derived table. Write a query to pick out only one record from the one to many table (your requirements should specify which record to pick). Join to that instead. OR you may be able to put further conditions on the left join to get only one record. Some examples of these techniques:

select t1.field1, t2.email
from table1 t1 
join (select myid, max(email) as email from table2 group by myid) t2 
  on t1.myid = t2.myid

Or

select t1.field1, t2.email
from table1 t1 
Left join from table2  t2 
  on t1.myid = t2.myid and t2.active = 1

Or if you want all of the emails in a comma delimited list, that code is database specific and you would need to let us know which database backend you are using.