| Post-select vs Post-Query [message #119184] |
Wed, 11 May 2005 01:29  |
vgs2005
Messages: 123
Registered: April 2005
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Senior Member |
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I was asked in an interview about the difference between
Post-select vs Post-Query. However, I have never heard (or used) Post-select before.. Can anyone tell me the answer?
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| Re: Post-select vs Post-Query [message #119189 is a reply to message #119184] |
Wed, 11 May 2005 01:54  |
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djmartin
Messages: 10181
Registered: March 2005
Location: Surges Bay TAS Australia
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Senior Member
Account Moderator |
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The Reference Guide states:
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Post-Select Trigger
Description
The Post-Select trigger fires after the default selection phase of query processing, or after the successful execution of the On-Select trigger. It fires before any records are actually retrieved through fetch processing.
Definition Level form or block
Legal Commands
SELECT statements, unrestricted built-ins
Enter Query Mode no
Usage Note:
Use the Post-Select trigger to perform an action based on the outcome of the Select phase of query processing such as an action based on the number of records that match the query criteria.
On Failure
no effect
Fires In
Execute the Query
Open the Query
Review Process Flowcharts
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Basically the post_select fires once per query. The post_query fires for every line.
I have only seen it used rarely. It could be used to execute the count_query command to determine the number of records to be retrieved. Use it to tell the user that too many rows had been selected. Often this task is done in the pre-query trigger where you do an explicit 'count' on the database and issue the message and fail before the true query is done.
[Updated on: Wed, 11 May 2005 02:01] Report message to a moderator |
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