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Data Warehousing Community Forum > Databases > Oracle > Topic: Differentiate b/n WHERE and HAVING BY
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unknown
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« on: December 14, 2007, 08:29:32 am »
Hi all

Can anyone please differentiate between WHERE and HAVING BY clause...?
When each of them can be used ?

Help is appreciated....
Thanks in Adv.
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ragjeevan
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« Reply #1 on: February 18, 2010, 01:01:41 pm »
Where is a filter executed at row level

Having by is a filter that is executed over aggregated data.
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sanjay81
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« Reply #2 on: May 05, 2010, 01:15:16 am »
HAVING clause is used when you want to specify a condition for a group function and it is written after GROUP BY clause. The WHERE clause is used when you want to specify a condition for columns, single row functions except group functions and it is written before GROUP BY clause if it is used.
Where is used to restrict the rows having is used to restrict the group.  Wink
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shanilr
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« Reply #3 on: May 18, 2010, 02:21:09 pm »
Hi Sanjay,

First of all you can use HAVING clause only with the Group by clause. So therefore Having clause is used to limit the records which are grouped  based on the specified columns. In a typical SQL statement WHERE clause gets executed first and then SQL processes Group by and Having clause. So Where clause can be used to filter out the records which are not needed for the Group by clause and then Having clause can be used to display only those records which meets the required condition after grouping.
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