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Beier Hints

Date post: 17-Aug-2015
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Presented Bywww.orienit.comHints give specifc information that we know about our data and application.A way to override the default query optimization in the DB!"n#uence the e$ecution plan of querywww.orienit.com%racle optimizer may not always choose the best e$ecution plan&sing hints may improve the performance by changing the e$ecution plan oracle takes.www.orienit.comHints can be used in the !elect' Delete' and &pdate clauses."n each statement' the hint goes directly after the !elect' Delete' or &pdate keyword.A few hints use "nsert.Hints are placed in the ()*)( tag' where the hint goes after the * sign+$, !+-+./ ()* A--01%2! )( 3rom4www.orienit.comApproach hintsAccess hints5oin hintsisc. hintswww.orienit.comA--01%2!, inimizes total resource consumption.1esults will be returned only after all processing has been completed3"1!/01%2!6n7, inimized response time' or minimal resource usage to return the frst n rows.www.orienit.com3&--6table7, .hooses a full table scan for the table' even if there is an inde$ available."8D+96table :inde$ :inde$;...;7, .hooses an "nde$ scan for the table.www.orienit.com."! Department has far more males than females!+-+./ ()* 3&--6s7 )( id' name 31% !tudent s2H+1+ se$ < =m>?!+-+./ ()* "nde$6s se$0inde$7 )( id' name31% !tudent s2H+1+ se$ < =f>?www.orienit.com%1D+1+D, tables are @oined in the order in which they appear in the 31% clause.-+AD"8A6table7, specifed table is the frst table used in the @oin order.&!+0HA!H6table :table; 47, /ables are @oined using a hash @oin.!maller table is used to make a hash table on @oin key. /he larger table is scanned using hash table to fnd @oined rows.www.orienit.com&!+08-6table :table;47, 5oins tables using nested loops @oin' using specifed table as inner @oin.3or every row in outer table' oracle accesses every row in inner table.&!+0+1A+6table :table;47, 5oins tables using a sortBmerge @oin.!orted list are made and then merged together.Best if tables are already sorted.www.orienit.comACC+8D, Data is appended to the end of table' rather then using e$isting space..A.H+6table7, Blocks received are placed at the most recently used end of the -1& list in the buDer cache when a full table scan is preformed.8%.A.H+6table7, Blocks received are placed at the least recently used end of the -1& list in the buDer cache.www.orienit.com%racle documentation at, http,((oracle.cis.ksu.edu(oradocs(inde$.htmwww.orienit.com


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