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abc
Starting Member
48 Posts |
 Posted - 2001-12-11 : 03:04:08
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| When read Book online, I try to understand the meaning of query hint, table hint, index hint, join hint.... And I really don't understand these's meaning. Tell me more about them plsThanks for your attention |
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mfemenel
Professor Frink
1421 Posts |
Posted - 2001-12-11 : 08:13:52
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| a hint is basically a way of telling sql server, "hey, instead of figuring it out on your own, do it this way". For example, SQL might create an execution plan for your query that you don't agree with. You can override it's choices by giving it hints as to how you would prefer it to behave. Generally, it's reccomended that you let SQL "do it's business" without your intervention. I would only reccomend you use hints if you're sure of what you're doing.Mike "A program is a device used to convert data into error messages." |
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JustinBigelow
SQL Gigolo
1157 Posts |
Posted - 2001-12-11 : 10:18:17
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quote:
I would only reccomend you use hints if you're sure of what you're doing.
I never get to use hints  Justin |
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abc
Starting Member
48 Posts |
Posted - 2001-12-12 : 01:53:02
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| Thanks for mfemene guide, could you give me an example to illutrate the different between use not use or not use table hint, query hint...Thanks for your attention |
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nr
SQLTeam MVY
12543 Posts |
Posted - 2001-12-12 : 07:50:30
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| hints were common in v6.5 - not so necessary in v7+ as the optimiser tends to be more reliable - still makes some glaring errors though.common hints are index, nolock and tablockx, holdlockselect * from tbl with (index=ix1, nolock)the index tells the optimiser to use this index (it may just use the index to scan if it's not useful.the nolock tells it not to take or honour locks - this is used to check what's happenning on a production system with deadlocking or slowing down the processing (much) or checking what is happenning within a transaction. Beware of using it in production code as it can produce strange results.Use tablockx, holdlock to exclusively lock a table for the duration of a transaction (don't forget the holldlock).option ...query hints restrict what type of plan is available to the optimiserMAXDOP is used to overcome bugs and fast is also possibly useful - I've suggested it to people but never heard about the outcome.==========================================Cursors are useful if you don't know sql.Beer is not cold and it isn't fizzy.Edited by - nr on 12/12/2001 07:55:10 |
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Doug G
Constraint Violating Yak Guru
331 Posts |
Posted - 2001-12-12 : 19:36:38
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quote:
quote:--------------------------------------------------------------------------------I would only reccomend you use hints if you're sure of what you're doing.--------------------------------------------------------------------------------I never get to use hints Justin
 ======Doug G====== |
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what is table_hint, .....