Sql server joining with aggregate functions

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I have following tables with data as given below

Batch-Information
-----------------
Batch-code	total-seats	
----------      -----------
b1		30
b2		25
b3		35
b4		40

Admission-Information
---------------------
Admno	Sname	Batch-code
-----   -----   ----------
1	a	b1
2	b	b3
3	c	b3
4	d	b3
5	e	b1
6	f	b4
7	g	b2
8	h	b4
9	i	b1
10	j	b2

I want to write a query to show the output as follows

C#

Batch-code	total-seats	Filled-Seats	Vacant-seats
----------      -----------     ------------    ------------
b1		30		3		27
b2		25		2		23
b3		35		3		32
b4		40		2		38

But I did not get how to count total seats filled seats vacant seats etc in query.
Thanks in advance for help

What I have tried:

C#

SELECT * FROM Admission-Information AA LEFT OUTER JOIN Batch-Information e2
ON AA.Batch-Code = BB.Batch-Code

Also tried count(*) But not successful

Posted 17-Jan-18 6:10am

CodeMine

Updated 18-Jan-18 22:25pm

OriginalGriff

v2

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2 solutions

Solution 2

SELECT Batchcode,
	totalseats,
	isnull((
			SELECT COUNT(1)
			FROM @AdmissionInformation a
			WHERE a.Batchcode = b.Batchcode
			GROUP BY Batchcode
			), 0) AS FilledSeats,
	totalseats - isnull((
			SELECT COUNT(1)
			FROM @AdmissionInformation a
			WHERE a.Batchcode = b.Batchcode
			GROUP BY Batchcode
			), 0) AS Vacantseats
FROM @BatchInformation b

Posted 18-Jan-18 22:25pm

Member 13632036

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OriginalGriff · Accepted Answer · 2018-01-17T06:59:00

Probably, you need to add a GROUP BY:

SQL

SELECT [Batch-Code], COUNT(*) AS Filled FROM [Admission-Information]
GROUP BY [Batch-code]

Will give you the "filled seats" you need, so then all you have to do is JOIN that:

SQL

SELECT b.[Batch-code] , b.[Total-Seats], fs.Filled, b.[Total-Seats] - fs.Filled AS [Vacant-seats]
FROM [Batch-Information] b
JOIN (SELECT [Batch-Code], COUNT(*) AS Filled FROM [Admission-Information]
      GROUP BY [Batch-code]) fs 
ON b.[Batch-code] = fs.[Batch-code]

Which will give you what you wanted.