Comments on: SQL SERVER – 2005 Explanation and Example – SELF JOIN

By: pinaldave

pinaldave — Mon, 24 Sep 2012 10:35:21 +0000

That is the point. Self join can be outer, inner or cross join and it is not of type of its own.

By: Anon

Anon — Mon, 24 Sep 2012 10:11:00 +0000

A self join is an example of an inner join, the code example even says inner join. I would not classify this as a ‘type of join’ in its own right.

By: Ranak

Ranak — Wed, 30 May 2012 07:38:55 +0000

good article

By: Manas

Manas — Tue, 13 Mar 2012 11:23:52 +0000

Really fantastic Dave,

By: Garima

Garima — Tue, 06 Mar 2012 11:42:37 +0000

nice nd very useful article.

By: Garima

Garima — Tue, 06 Mar 2012 11:37:39 +0000

nice article

By: sayan

sayan — Tue, 29 Nov 2011 11:54:41 +0000

i want to display data on text box and few of label from two tables emp_master and formula besis of selection of emp_no in combo box, i write down follwing code..bt no data show on textbox and label. any body help …….plz…….

Dim con As New SqlConnection(“Data Source=MICRODAT-39F82C;Initial Catalog=master;Integrated Security=SSPI”)

Dim Da As New SqlDataAdapter
Dim Da1 As New SqlDataAdapter
Dim Ds As New DataSet
Dim Ds1 As New DataSet
Dim Dt As New DataTable
Dim Dt1 As New DataTable
con.Open()

Try

Da = New SqlDataAdapter(“Select f.Basic_sal,f.d_a,f.p_p,f.c_a,f.h_r_a,f.medical,f.o_a,f.o_t,f.p_f,f.o_p_f,f.loan,f.ad_vance,f.s_s_s,f.elec_charge,f.p_tax,f.i_tax,f.e_s_i,f.gross_sal,f.net_sal,f.date,e.emp_name,e.d_o_b,e.sex,e.d_o_j,e.gard_name,e.present_add from farmula f INNER JOIN emp_master e ON f.emp_no=’” & ComboBox1.SelectedValue.ToString & “‘where e.emp_no=f.emp_no “, con)

Da.Fill(Ds)
Catch ex As Exception
MessageBox.Show(ex.Message)

TxtBx_EBsic.Text = Ds.Tables(0).Rows(0).Item(“f.Basic_sal”).ToString
TxtBx_DA.Text = Ds.Tables(0).Rows(0).Item(“f.d_a”).ToString
TxtBx_PP.Text = Ds.Tables(0).Rows(0).Item(“f.p_p”).ToString
TxtBx_HRA.Text = Ds.Tables(0).Rows(0).Item(“f.h_r_a”).ToString
TxtBx_Medi.Text = Ds.Tables(0).Rows(0).Item(“f.medical”).ToString
TxtBx_CA.Text = Ds.Tables(0).Rows(0).Item(“f.c_a”).ToString
TxtBx_OA.Text = Ds.Tables(0).Rows(0).Item(“f.o_a”).ToString
TxtBx_OT.Text = Ds.Tables(0).Rows(0).Item(“f.o_t”).ToString
TxtBx_Grssal.Text = Ds.Tables(0).Rows(0).Item(“f.gross_sal”).ToString
TxtBx_pf.Text = Ds.Tables(0).Rows(0).Item(“f.p_f”).ToString
TxtBx_Opf.Text = Ds.Tables(0).Rows(0).Item(“f.o_p_f”).ToString
TxtBx_ptax.Text = Ds.Tables(0).Rows(0).Item(“f.p_tax”).ToString
TxtBx_esi.Text = Ds.Tables(0).Rows(0).Item(“f.e_s_i”).ToString
TxtBx_BLne.Text = Ds.Tables(0).Rows(0).Item(“f.loan”).ToString
TxtBx_adv.Text = Ds.Tables(0).Rows(0).Item(“f.ad_vance”).ToString
TxtBx_elec.Text = Ds.Tables(0).Rows(0).Item(“f.elec_charge”).ToString
TxtBx_sss.Text = Ds.Tables(0).Rows(0).Item(“f.s_s_s”).ToString
TxtBx_IT.Text = Ds.Tables(0).Rows(0).Item(“f.i_tax”).ToString
TxtBx_netpay.Text = Ds.Tables(0).Rows(0).Item(“f.net_sal”).ToString
txtbx_dt.Text = Ds.Tables(0).Rows(0).Item(“f.date”).ToString
Label56.Text = Ds.Tables(0).Rows(0).Item(“e.emp_name”).ToString
Label9.Text = Ds.Tables(0).Rows(0).Item(“e.sex”).ToString
Label13.Text = Ds.Tables(0).Rows(0).Item(“e.d_o_b”).ToString
Label57.Text = Ds.Tables(0).Rows(0).Item(“e.present_add”).ToString
Label1.Text = Ds.Tables(0).Rows(0).Item(“e.gard_name”).ToString
Label15.Text = Ds.Tables(0).Rows(0).Item(“e.d_o_j”).ToString

End Try
con.Close()

By: SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 4 of 31 Journey to SQLAuthority

Mon, 04 Jul 2011 01:31:49 +0000

[...] This is a particular case when one table joins to itself with one or two aliases to avoid confusion. A self join can be of any type, as long as the joined tables are the same. A self join is rather unique in that it involves a relationship with only one table. The common example is when company has a hierarchal reporting structure whereby one member of staff reports to another. Self Join can be Outer Join or Inner Join. (Read more here) [...]

By: Francis D

Francis D — Thu, 30 Jun 2011 16:45:26 +0000

Hi Pinal Dave

your blog is very useful. encourage all to alway visit this site for reference.
keep it up.

By: Anas Teinah

Anas Teinah — Tue, 21 Dec 2010 02:33:53 +0000

i think u dont need self join to answer the query
“find products that are supplied by more than one vendor”

here is my solution

SELECT ProductID, count(VendorID) as “Num OF Vendors”
FROM Purchasing.ProductVendor pv1
GROUP BY ProductID
HAVING count(VendorID) > 1
ORDER BY ProductID

thank u in advance

By: siddu

siddu — Wed, 15 Dec 2010 18:22:08 +0000

me 2.. :)

By: naresh

naresh — Mon, 22 Nov 2010 10:10:50 +0000

really i like ur response

By: ASHOK

ASHOK — Thu, 12 Aug 2010 05:13:12 +0000

dear sir
your articles are really very use full for all users .
thanks a lot for create it.

By: danish khan

danish khan — Fri, 16 Jul 2010 07:12:30 +0000

it works efficiently

By: SQL SERVER – The Self Join – Inner Join and Outer Join Journey to SQL Authority with Pinal Dave

Thu, 08 Jul 2010 01:32:19 +0000

[...] be the outer join, I often get a request for an example for the same. I have created example using AdventureWorks Database of Self Join earlier, but that was meant for inner join as well. Let us create a new example today, where we [...]

By: Paul

Paul — Thu, 20 May 2010 18:28:04 +0000

some of you (Srinu, Pravin) are not reading all the comments. Clive Paterson has the solution about eliminating the duplicate records in his comment. So simple.

as Clive said:

“Using less than in the join will eliminate the duplicate results:”

meaning join on the record1.ID < record2.ID as part of your join.

clive's comment:
http://blog.sqlauthority.com/2007/06/03/sql-server-2005-explanation-and-example-self-join/#comment-52507

By: Srinu

Srinu — Wed, 19 May 2010 06:59:44 +0000

Result iam getting like this.

00002323560 00002323560 189.00000 213.88000
00002323560 00002323560 200.34000 213.88000
00002323701 00002323701 374.39999 399.70001
00002323704 00002323704 3533.33008 3997.00000
00002323704 00002323704 3744.00000 3997.00000
00002323730 00002323730 106.00000 119.91000
00002323730 00002323730 112.32000 119.91000
00002323733 00002323733 353.32999 399.70001
00002323733 00002323733 374.39999 399.70001
00002323734 00002323734 112.32000 119.91000

By: Srinu

Srinu — Wed, 19 May 2010 06:57:30 +0000

hi Pinal Dave,

i have a doubt in self join,

i have written query like this.

SELECT DISTINCT R.NDC,R1.NDC,
R.NPT_PRICEX as LastPrice,
R1.NPT_PRICEX as NewPrice,
from RNP2_NDC_PRICE R
join
RNP2_NDC_PRICE R1
on R1.NDC=R.NDC
and R1.IsActive=’TRUE’
and R.IsActive=’FALSE’

iam getting duplicate records through this query,because
the table having more than one non active records with same NDC.

please help me to avoid duplicate records.

By: Aseem

Aseem — Fri, 29 Jan 2010 11:32:05 +0000

you are man of vision

By: hassum

hassum — Sat, 23 Jan 2010 04:27:37 +0000

I’d like to make a qury to give me back the confliction beween starttime and endtime and the period between them,

i want to insert a new field to Lecture table so that it must be not conflicted with the time of other lecture for the same teacher .

thank for help.

By: Brian Tkatch

Brian Tkatch — Wed, 16 Dec 2009 15:17:42 +0000

@Pravin

DISTINCT works on the entire record, not just one COLUMN.

Something likw: select ename, MAX(salary) from employee GROUP BY ename; might work for you.

By: Pravin

Pravin — Wed, 16 Dec 2009 05:57:02 +0000

When we select multiple columns with Distinct as Clause
it does not gives distinct values Please see below Eg.

Employee is the Table with values

Santosh Patil 19000
Shilpa Shinde 18000
Ajit 20000
Pramod 15000
Pravin 21000
Prakash 15000
Ajit 35000

Query is

select distinct ename,salary from employee

O/P show is

Ajit 20000
Ajit 35000
Prakash 15000
Pramod 15000
Pravin 21000
Santosh Patil 19000
Shilpa Shinde 18000

Here there is Duplication of Name Ajit.

Plz Help me in sorting out this Problem.

Awaiting for Your Favourable reply.

Regards.

By: Chandraakant H P

Chandraakant H P — Fri, 04 Dec 2009 06:51:39 +0000

Nice and important article about self join,really its informative.

By: Sanda

Sanda — Wed, 24 Jun 2009 04:57:21 +0000

I have one observation regarding the example you gave:

USE AdventureWorks;
GO
SELECT DISTINCT pv1.ProductID, pv1.VendorID
FROM Purchasing.ProductVendor pv1
INNER JOIN Purchasing.ProductVendor pv2
ON pv1.ProductID = pv2.ProductID
AND pv1.VendorID = pv2.VendorID
ORDER BY pv1.ProductID

You said it will “find products that are supplied by more than one vendor”. This query returns all products from the table, not just the ones supplied by 2 or more vendors

Maybe you meant something more like this ( instead of =)

or even

USE AdventureWorks;
GO
SELECT DISTINCT pv1.ProductID
FROM Purchasing.ProductVendor pv1
INNER JOIN Purchasing.ProductVendor pv2
ON pv1.ProductID = pv2.ProductID
AND pv1.VendorID pv2.VendorID
ORDER BY pv1.ProductID

By: Clive Paterson

Clive Paterson — Thu, 28 May 2009 09:33:37 +0000

Using less than in the join will eliminate the duplicate results:

USE AdventureWorks;
GO
SELECT DISTINCT pv1.ProductID, pv1.VendorID
FROM Purchasing.ProductVendor pv1
INNER JOIN Purchasing.ProductVendor pv2
ON pv1.ProductID < pv2.ProductID
AND pv1.VendorID < pv2.VendorID
ORDER BY pv1.ProductID1

Image the results set as a square grid where every row from pv1 is join with every row from pv2. Now, using a less than in the join will only join row from pv2 which have an ID greater than the ID in pv1, eliminating duplicates:

       pv2

     0 0 0 0 0 0
     x 0 0 0 0 0
p   x x 0 0 0 0
v   x x x 0 0 0
1   x x x x 0 0
     x x x x x 0