Need help in building a SQL query?

Question

Need help in building a SQL query?

dreampoo7

Newbie

Points: 5
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September 16, 2013 at 1:42 pm

#283214

Hi Experts,
I have table called "Entries" having general information of Employees as...
TableName: Entries
Select * from Entries where mskey = 1234
MSKEY, ATTRNAME, AVALUE
1234, NUMBER, 3
1234, FNAME, DAVID
1234, MNAME, M
1234, LNAME, HUDSON
Select * from Entries where mskey = 2345
MSKEY, ATTRNAME, AVALUE
2345, NUMBER, 5
2345, FNAME, MARK
2345, LNAME, WOOD
2345, EMAIL, mwood@email.com
NOTE: MSKEY is the Primary Key for the table Entries. NUMBER is also primary key.
I need to write a SQL query and the output should look like...
NUMBER, FNAME, MNAME, LNAME, EMAIL
1234, DAVID, M, HUDSON, NULL (Blank)
2345, MARK, NULL (Blank), WOOD, mwood@email.com
I did a SQL query as...
select a.avalue as [NUMBER], b.avalue as [FNAME], c.avalue as [MNAME],
d.avalue as [LNAME], e.avalue as
from Entries.a, Entries.b, Entries.c, Entries.d, Entries.e
where a.mskey = b.mskey and b.mskey = c.mskey and c.mskey = d.mskey and
d.mskey = e.mskey and a.attrname = 'NUMBER' and b.attrname = 'FNAME' and
c.attrname = 'MNAME' and d.attrname = 'LNAME' and e.attrname = 'EMAIL' and
a.mskey in
(select mskey from Entries where avalue in ('1234','2345'))
Please help me to write a SQL query using the table "Entries". Thanks in advance.
Regards,
Arun
Forum Etiquette: How to post Reporting Services problems

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Forum Etiquette: How to post data/code on a forum to get the best help - by Jeff Moden
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How to Post Performance Problems - by Gail Shaw
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Sean Lange SSC Guru Points: 286573 More actions · Answer 1

Hi and welcome to the forums. It is difficult to provide you a lot of direction because you didn't provide ddl and sample data for the table. Please take a few minutes and read the first article in my signature for best practices when posting questions.

One thing I can say for sure. You have an EAV "design" pattern. This is one of the most difficult patterns to work with and the performance can horribly wrong very quickly.

I would recommend that you use ANSI-92 style joins instead of the ANSI-89 style joins. They are easier to read and less prone to accidental cross joins.

_______________________________________________________________

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Cross Tabs and Pivots, Part 1 – Converting Rows to Columns - http://www.sqlservercentral.com/articles/T-SQL/63681/
Cross Tabs and Pivots, Part 2 - Dynamic Cross Tabs - http://www.sqlservercentral.com/articles/Crosstab/65048/
Understanding and Using APPLY (Part 1) - http://www.sqlservercentral.com/articles/APPLY/69953/
Understanding and Using APPLY (Part 2) - http://www.sqlservercentral.com/articles/APPLY/69954/

Alan Burstein SSC Guru Points: 61136 More actions · Answer 2

Below is some DDL and a solution:

--DDL

USE tempdb

IF OBJECT_ID('tempdb..Entries') IS NOT NULL DROP TABLE Entries;

CREATE TABLE Entries (MSKEY int, ATTRNAME varchar(20), AVALUE varchar(20), primary key (MSKEY, ATTRNAME));

INSERT Entries (MSKEY, ATTRNAME, AVALUE)

SELECT 1234, 'NUMBER', '3' UNION ALL

SELECT 1234, 'FNAME', 'DAVID' UNION ALL

SELECT 1234, 'MNAME', 'M' UNION ALL

SELECT 1234, 'LNAME', 'HUDSON' UNION ALL

SELECT 2345, 'NUMBER', '5' UNION ALL

SELECT 2345, 'FNAME', 'MARK' UNION ALL

SELECT 2345, 'LNAME', 'WOOD' UNION ALL

SELECT 2345, 'EMAIL', 'mwood@email.com';

--OUTPUT

SELECT DISTINCT

e.MSKEY AS NUMBER,

ISNULL(fn.AVALUE,'') AS FNAME,

ISNULL(mn.AVALUE,'') AS MNAME,

ISNULL(ln.AVALUE,'') AS LNAME,

ISNULL(em.AVALUE,'') AS EMAIL

FROM Entries e

LEFT JOIN Entries fn

ON e.MSKEY=fn.MSKEY AND fn.ATTRNAME='FNAME'

LEFT JOIN Entries mn

ON e.MSKEY=mn.MSKEY AND mn.ATTRNAME='MNAME'

LEFT JOIN Entries ln

ON e.MSKEY=ln.MSKEY AND ln.ATTRNAME='LNAME'

LEFT JOIN Entries em

ON e.MSKEY=em.MSKEY AND em.ATTRNAME='EMAIL'

The solution I provided is not optimal - it uses a very expensive DISTINCT. I'm going to try to put together a faster query (unless someone beats me to it) . This will, however, get you the results you need.

"I cant stress enough the importance of switching from a sequential files mindset to set-based thinking. After you make the switch, you can spend your time tuning and optimizing your queries instead of maintaining lengthy, poor-performing code."

-- Itzik Ben-Gan 2001

Alan Burstein SSC Guru Points: 61136 More actions · Answer 3

This could still be optimized but will perform a little better than my previous query:

--OUTPUT

SELECT e.MSKEY AS NUMBER,

ISNULL(fn.AVALUE,'') AS FNAME,

ISNULL(mn.AVALUE,'') AS MNAME,

ISNULL(ln.AVALUE,'') AS LNAME,

ISNULL(em.AVALUE,'') AS EMAIL

FROM Entries e

LEFT JOIN Entries fn

ON e.MSKEY=fn.MSKEY AND fn.ATTRNAME='FNAME'

LEFT JOIN Entries ln

ON e.MSKEY=ln.MSKEY AND ln.ATTRNAME='LNAME'

LEFT JOIN Entries mn

ON e.MSKEY=mn.MSKEY AND mn.ATTRNAME='MNAME'

LEFT JOIN Entries em

ON e.MSKEY=em.MSKEY AND em.ATTRNAME='EMAIL'

WHERE e.ATTRNAME=fn.ATTRNAME

"I cant stress enough the importance of switching from a sequential files mindset to set-based thinking. After you make the switch, you can spend your time tuning and optimizing your queries instead of maintaining lengthy, poor-performing code."

-- Itzik Ben-Gan 2001

mister.magoo SSC-Forever Points: 47068 More actions · Answer 4

There is no need for all those joins.

select e.MSKEY

, max(case when e.ATTRNAME='FNAME' then e.AVALUE end) AS FNAME

, max(case when e.ATTRNAME='MNAME' then e.AVALUE end) AS MNAME

, max(case when e.ATTRNAME='LNAME' then e.AVALUE end) AS LNAME

, max(case when e.ATTRNAME='EMAIL' then e.AVALUE end) AS EMAIL

from Entries AS e

group by e.MSKEY

MM

select geometry::STGeomFromWKB(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

Jeff Moden SSC Guru Points: 1003857 More actions · Answer 5

Just to backup Maggo's solution... the method he used is called a "CROSSTAB". You could also use a PIVOT although the CROSSTAB solution is usually a touch faster. Such a solution is one of the better ones because it only has to make a pass at the table one time. To wit, it's a common solution for "pivoting" EAV tables of this nature.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

Alan Burstein SSC Guru Points: 61136 More actions · Answer 6

Well done Magoo; I knew there was a much better way but drew a blank.

Jeff Moden (9/16/2013)
Just to backup Maggo's solution... the method he used is called a "CROSSTAB". You could also use a PIVOT although the CROSSTAB solution is usually a touch faster. Such a solution is one of the better ones because it only has to make a pass at the table one time. To wit, it's a common solution for "pivoting" EAV tables of this nature.

I wish I had read Cross Tabs and Pivots, Part 1 – Converting Rows to Columns[/url] before putting my query together.

"I cant stress enough the importance of switching from a sequential files mindset to set-based thinking. After you make the switch, you can spend your time tuning and optimizing your queries instead of maintaining lengthy, poor-performing code."

-- Itzik Ben-Gan 2001

Jeff Moden SSC Guru Points: 1003857 More actions · Answer 7

Alan.B (9/17/2013)
Well done Magoo; I knew there was a much better way but drew a blank.
Jeff Moden (9/16/2013)
Just to backup Maggo's solution... the method he used is called a "CROSSTAB". You could also use a PIVOT although the CROSSTAB solution is usually a touch faster. Such a solution is one of the better ones because it only has to make a pass at the table one time. To wit, it's a common solution for "pivoting" EAV tables of this nature.
I wish I had read Cross Tabs and Pivots, Part 1 – Converting Rows to Columns[/url] before putting my query together.

🙂

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)