Databases
StackOverflow2013
Postsdbo
PO
 

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  1. PO
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    <p>Use count, like</p> <p>select count(*) from enemies where monsterid = 334322</p> <p>However be sure to make certain you've added an index on monsterid to the table. Reason being that if you don't, and this isn't the primary key, then the rdbms will be forced to issue a full table scan - read every row - to give you the value back. On small datasets this doesn't matter as the table will probably sit in core anyway, but once the number of rows becomes significant and you're hitting the disk to do the scan the speed difference can easily be two orders of magnitude or more.</p> <p>If the number of rows is <em>very</em> small then not indexing is rational as using an non-primary key index requires additional overhead when inserting data, however this should be a definite decision (I regularly impress clients who've used a programmer who doesn't understand databases by adding indexes to tables which were fine when the coder created them but subsequently slow to a crawl when loaded with real volumes of data - quite amazing how one line of sql to add an index will buy you guru status in your clients eyes cause you made his system usable again).</p> <p>If you're doing more complex queries against the database using subselect, something like finding all locations where there is no monster, then look up the use of the sql EXISTS clause. This is often overlooked by programmers (the temptation is to return a count of actual values) and using it is generally faster than the alternatives.</p>
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    1. POchecking to see if data exist with in a table
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    1. PTAnswer
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    1. USCruachan
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    1. COI will definitely look into the EXISTS clause. thank you for the advice.
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      1. USJesse
 

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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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