Why and How to write SQL Sub queries

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I was wondering if someone could give me an example of a SQL Sub query with a table schema and a reason for doing it.

I saw this at my previous company SELECT ( Select * from ) ...something like that. I have never used sub queries before and I'm wondering what purpose they serve .. I have no idea what the previous programmer who wrote the sub query was trying to do but I know that you can write sub queries. I just have no idea why .

Any example would be appreciated.

Posted 1-Aug-11 12:05pm

UBX

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3 solutions

Solution 2

subQuries[^]

Posted 2-Aug-11 1:26am

uspatel

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[no name] 2-Aug-11 10:42am

thks

Solution 4

If You want a column or a value or a single where condition data then you can use sql sub query instead of writing complex join etc.

Ex 1. Select name,gender,(Select top 1 schoolname from abc where xyzid = 1) from xyz where id=1

Ex 2. Select name,gender from xyz where id=(select max(id) from xyz)

Ex 3. Select abcxyz.Name from (select id,Name from xyz
where id=(select max(id) from xyz) ) abcxyz;

You can learn from [^here]

Posted 25-Sep-14 22:46pm

Jems_007

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thatraja · Accepted Answer · 2011-08-01T12:28:00

Solution 1

Read this
The Power of Subqueries[^]

Posted 1-Aug-11 12:28pm

thatraja

Comments

walterhevedeich 1-Aug-11 19:26pm

Nice link.

[no name] 2-Aug-11 10:42am

thks

thatraja 2-Aug-11 10:44am

You welcome