April 28, 2010 at 2:49 am
Please explain different between the queries
SELECT *
FROM EmpAddress addr
LEFT JOIN EmpEducation edu
ON addr.empid = edu.empid
--WHERE EDU.EMPID IS NULL
WHERE addr. AddType = 2
SELECT *
FROM EmpAddress addr
LEFT JOIN EmpEducation edu
ON addr.empid = edu.empid AND addr. AddType =
April 28, 2010 at 3:02 am
Is this Left outer join?
If yes.
1. "addr.empid = edu.empid"-----This is join condition
2. "addr. AddType = 2"----This is filter condition
filter condition should not be mixed with join condition. But in this scenario there should not be any difference in the resultset of both.
April 28, 2010 at 5:10 am
vinodpec (4/28/2010)
Please explain different between the queriesSELECT *
FROM EmpAddress addr
LEFT JOIN EmpEducation edu
ON addr.empid = edu.empid
--WHERE EDU.EMPID IS NULL
WHERE addr. AddType = 2
SELECT *
FROM EmpAddress addr
LEFT JOIN EmpEducation edu
ON addr.empid = edu.empid AND addr. AddType =
the 1st query will show only results where from empaddress where addtype=2 - it will then join edu table and show those fields as well (but will not use this to limit rows returned)
the second query will will show all records from empaddress regardless off addtype and will then join edu table and show any related data - again it will not be used to filter the record set
query 1 will return less records
query 2 will have more blank data in the columns for edu table where the addr table <>2
MVDBA
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