CREATE TABLE #DEL2(ID INT IDENTITY(1,1),VALUE VARCHAR(MAX),FLAG CHAR(1))

INSERT INTO #DEL1 VALUES(’1ST’,1),(’2ND’,1),(’3RD’,2),(’4TH’,1),(’5TH’,2),(’6TH’,1)

INSERT INTO #DEL2 VALUES(’1ST’,1),(’2ND’,1),(’3RD’,2),(’4TH’,2),(’5TH’,2)

SELECT * FROM #DEL1
SELECT * FROM #DEL2

—————————————————————
– LEFT JOIN with Additional Condition on ON clause
SELECT *
FROM #DEL1 A
LEFT JOIN #DEL2 B ON A.ID=B.ID AND B.FLAG=1
—————————————————————
/* EQUILENT TO THIS QRY */
SELECT *
FROM #DEL1 A
LEFT JOIN (SELECT * FROM #DEL2 WHERE FLAG=1) B ON A.ID=B.ID
/* SO I OBSERVED THAT HERE ORDER OF EXECUTION IS FROM ,()PARANTHESIS,ON */
—————————————————————

/*
NOTE : LEFT OUTER JOIN MEANS THAT MATCHING THE VALUES OF RIGHT SIDE TABLE AND UNMATCHING VALUES OF LEFT SIDE TABLE
.SO NOW THE QRY WILL BE LIKE THIS

*/
—————————————————————
SELECT *
FROM
(
SELECT * FROM #DEL2 WHERE FLAG=1
) A
LEFT JOIN
(
SELECT * FROM #DEL1
) B ON A.ID=B.ID AND A.FLAG=1
—————————————————————
/* EQUILENT TO THIS QRY */
SELECT *
FROM #DEL1 A
LEFT JOIN #DEL2 B ON A.ID=B.ID
WHERE B.FLAG=1
—————————————————————
–CLEAN UP THE TABLES
DROP TABLE #DEL1
DROP TABLE #DEL2

A outer join keeps all records of the outer table and fill in data on the outer table based on the on condition. if there is not a match in the on condition data will not be joined on the outer table.

This is how I understand it and mabe it can help others

Select a.EmpNo , b.Description
from #temp1 a INNER JOIN #temp2 b
on (a.BadgeID = b.BadgeID OR A.BadgeID IS NULL)

SELECT *
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.ID = t2.ID AND t1.Flag = 1″

Even i have this question.. Did you get any solution for this?

Today, I had question using conditions within ON clause and I landed up here; This article is exactly my question and your explanation was superb but….. the part which I did not understood and challenge I am facing is ..

What if I apply conditions on first table
relating to your above example –
SELECT *
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.ID = t2.ID AND t1.Flag != 1 — or using t1.Flag = 2

I expected the result to be:
T1 T2
Value Flag Value Flag
Third 2 Third 2
Fifth 2 Null Null
Seventh 2 Null Null

but its also returning all values of table-1 with Flag =1 and joining with table – 2.

I did not run your tables but I have a similar example. Please guide me if I am missing anything; I thought using condition within ON clause improves performance since it reduces the number of rows to be joined based on the conditions. Please suggest and clarify.

Thanks,
Sam.

Any way, .. thanks…. for your try..

I need to get TextDescription from Master table for the corresponding ID in transaction table.
Thats all the concept.. if the corresponding ID is not available in Master table.,, we have to omit that record While fetching from Trasaction table.

Thats it………..

EmpNo Description
————————–
1 Mixing
2 Simplex

If it is so, then you can try out the query this way:

SELECT a.EmpNo , b.Description FROM #temp1 a
INNER JOIN #temp2 b ON a.EmpNo = b.BadgeID

Regards,
Raghav

Create table #temp2(BadgeID int Identity Not NUll, Description varchar(20) Not NUll)
Insert into #temp2 values ( ‘Mixing’)
Insert into #temp2 values ( ‘Simplex’)
Insert into #temp2 values ( ‘Combing’)
Insert into #temp2 values ( ‘Adidas’)

Delete from #temp2 where Description = ‘Combing’

——————————————–

Select * from #temp1

Result:
EmpNo BadgeID
1 1
2 NULL
3 3
———————————————

Select * from #temp2

Result :
BadgeID Description
1 Mixing
2 Simplex
4 Adidas
——————————————–

Select a.EmpNo , b.Description from #temp1 a
left outer join
#temp2 b on a.BadgeID = b.BadgeID

Result:
EmpNo Description
1 Mixing
2 NULL
3 NULL

From the above Result, i want to eliminate the last record EmpNo = 3, since its Corresponding BadgeID 3 is not in table #temp2.

I want the result as :

EmpNo Description
1 Mixing
2 NULL

update t1
set t1.col=t2.col
from table1 as t1 inner join table2 as t2 on t1.keycol=t2.keycol
where t2.somecol=

SELECT *
FROM Table1 t1
INNER JOIN Table2 t2 ON t1.ID = t2.ID

Thank you

Regards
janani.S

My Issue is , i want to eliminate records if ID is not available in table t2

Note : t1.Id is Nullable Column in table t1
t2.Id is Not Nullable and Identity Column in table t2

SELECT *
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.ID = t2.ID WHERE t2.Flag is null

Please Give me Solution for the below Problem!!!!!!!!

SELECT *
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.ID = t2.ID AND t2.Flag is null

———-

How To Hanle the Query…

If i want want to eliminate Resultant Record when t2.Id is Not Available in Table t2 and t1.Id is Not Null from the above Query Result

Note : t1.Id is Nullable Column in table t1
t2.Id is Not Nullable and Identity Column in table t2

Please Give me Solution for the below Problem!!!!!!!!

SELECT *
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.ID = t2.ID AND t2.Flag is null

———-

How To Hanle the Query…

If i want want to eliminate Resultant Record when t2.Id is Not Available in Table t2 and t1.Id is Not Null from the above Query Result

———-

How To Hanle Left Join …
If i want want to eliminate Resultant Record when t2.Id is Not Available in Table t2 from the above Query Result

But we do all make mistakes with grammar and punctuation at times, especially when there is no spelling or grammar checker. For example, you failed to punctuate the word ‘however’ correctly in your comment and misplaced the period as well. Your sentende should have read:

(Effect can also be an adjective depending on how it is used; however, affect is always a verb os it is doing something to something else.)

So it goes. I think the meaning of your comment as well as the meaning of Pinal Dave’s title are completely clear. So I would call your comment and mine both nitpicks.

:>)

I am very very glad to have your email and comment. I value and appreciate it 100%. Only friends give feedback.

I realise that English is not your main language and totally admire your ability to master it and write such fantastic articles using it. I hope that you are not offended to be informed of this slight error in what is a very misunderstood area of the language.

“SQL SERVER – Interesting Observation of ON Clause on LEFT JOIN – How ON Clause Effects Resultset in LEFT JOIN”

Should be

“SQL SERVER – Interesting Observation of ON Clause on LEFT JOIN – How ON Clause affects Resultset in LEFT JOIN”

The difference being the word Affects (Effects).
Affect is a verb where one thing affects another.
Effect is a noun where we see the effect that one thing had on the other.
(Effect can also be an adjective depending on how it is used however affect is always a verb os it is doing something to something else).

I think you have done a really good job of explaining the issue. I have often had to explain this weird behaviour to DB developers but in future I think I will simply point them at your example.

Regards

Dave

Your article saved me from committing a big mistake while writing a query.

Thanks for the good work

i have one query
i want to update the data in table 1 based on certain condition which must be satisfy by table 2 how should i do this please give small example
waiting for u r reply

thanks