sql查询语句的优化

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SQL查询语句的优化19???B4?7??z?????????????.19,No.42006??12?2JOURNALOFXINXIANGEDUCATIONCOLLEGEVb1DEC,2006SQL??????????wTz??q??(?zzW?????e?????g????zR???J???O???C???Z430079)????:???y????????zc??zu???????>SQL??????????wT?D?O?b??w??r?;?EP1??w???w??Q?;????P1???y?????x?????Z?????O??z??0?`???????????e??P9???<??:??????;SQL;????????;wT?D????zW???N????:M11???<?o???1:A?????D??:1672-3325(2006)04-0085-02???????b????z??????>??z??????????p???O?O??????zWzu???>w??rSQL??????????????w???P9???'??????zW???????????O??????????wT?D?Y?Lzt??????????????????????????P9???r???b?r?aw??rSQLServer??????wT?D?????q???????e???O[I]w"?>w??r????wT?D????zU???????D???????D??SE-LECT?????O??z`?D????????????z??????>???Y?D?Jz????????LP9?r???O????????z?zJ?O??z??0?b??zU?O?????t???A?O?O?r??????zWzU?O???????A???p???7???>?[?gzU?O?O???r??????????zRwT?D??????????zK?????7?????]?b????z????P???/xU?O?'z??D??SELECT??????wT??wb???????????????e??P9????z?????z??b???b????????wT?D?D??SELECT?????????Oz??O?????????7??P9z?P1wT?D????(z?)?2?N??????w??r?;?E ?????;?E?>?????????????7?????0?`?K??P9???r?a??z??q???????S???????;?E?????2?;?EP9?????;?E?>?o?;?E????????zR??zW?????????N????z??????;?E????P9?????O?r?????;?EzJ???p?4?????????O?q????z??????I?Y?????????4???????????O?g?R???r???????4???????????????Y??z????L???????=?O???yz????:????????????????zW?'?0?????????Oz??O?v??z?????????P9w"?>??zU?>?'?0???????9?r???o?;?E?O?b?d?rzJ??????????zJ???????o?;?E:??zW?C?????????n??P1???DzU???/;w??rBETWEEN,<P1<z?P1>L.>z??I?????p?4??x_??????;???/w??r?????DGROUPBY?x?????????CP9?r?bz[?C???p???????Ow??r???2?;?E??z??r??zW?????????????O???F???????????????O?????????`??P9w"?>w??r???2?;?E???????A?????N?;?E???Q??????P9w????O?rsno,cno??z6?????>z??;?E?OSELECTCOUNT(?O)FROMSCWHEREgrade>60ANDgrade<90;?r??z[????????zW?;?E??.P1cno???0?,?]?OqEE:RE?x??zW??grade???O??z`?YzUwb?v?r?;?E?????????????7??P9??z??b???rWHERE?x???R????)TSnoLSNOTNULL?O???a???d?7??z????;?E???Ez?????zW?O???L?;?E?????O???????p?7??P9(z?)??w?z?z???w????Q?;????z??B?>?1SQL???????e??????????????????w??rz?z[??z??L?B??wT?D???Ozt??????????w?z?z[??w??????p????P9wT?D???b????????????w????p?????O???r??????????w??????e???e?e????P9?r?bz[?????????????O??????w?z?z???w????Q?;?????Ow?wT?D???0???b???0??w??PP9w????O[3]SELECTstudent.student_name,student_~.course_??student_course.gradeFROMstudent,student_courseWHEREstudent.student_idz?)T??940202'ANDstudent.student_ idz?student_course.student_id;SELECTstudent.student_name,student_course.course_id,student_course.gradeFROMstudent,??tudent_courseWHEREstudent.student_??z?)T???a????)VANDstudent.student_idz?student_~.student_idANDstudent_z?.student_idz?)TS940202';?y????z-z[????????w??r?>???O???Ow"?>?Rz?z[??w?z????e?????u?e?Ow?z?????P9(z0)???yw??r?????x?????????x?????>?o?x????????????z?w???z??D?=?g????????z[???ex_P9?????x?????????=????zR?D?=?????0???O?'z????????U???p?O??z??D?=????????z?z[?f?????????pz??y???=???????????O??zG?????????g???????Cx_?q??zK?R?O?x??????????????z??:P9???awb?????e???????t????I/0??w??Ow????????????`????wz?O?OzG?p???=?:???b?O?`????wzP9?b?d??z?w??r??????????z??????x????;?????x????zU?????y?O??z`???r?x????zW???????m?????b???????pP9w????OSELECTsnameFROMstudentWHEREEXIST(SELEECI?g?i???7z?2006-05-22w??,??z?:?q??(1977-)?O???O??????z?z??O?zzW?????e?????????JzIzb2006???r???????G???7?O?????e??w??????J???????2P9?G???F:??z?????P92006??)TFROMSCWHEREstudent.snoz?SC.sno);??z??qzt????????SELECTsnameFROMstudent,SCWHEREstudent.sno=SC.sno;???a?O??z??1?????????b?????????pP9(??)???yw??rzU???????????????r??????????WHERE?x??zW??????float,int,char??varchar???>zU???????O??????????zU????????w?wT?D?????????pz?z??B????z????p??wT?D??w?P9w????OSELECTsno,snameFROMstudentWHEREsage>18;?rstudent??zW?Osage?????>???8???O?O18?>???????OwT?D?? ???????????pwT?D?ODBMS???`?N18???Dzt???8???R?y??zRsage????????P9?D?J???O???N18???D?L???8???????t?O??"SELECTsno,snameFROMstudentWHEREsagePJ)T18"'0(z?)???yw??r)Q<>)(?D)Q!z?)(?D)QNOT'?O???a???????8)Q<>)(?>?????e????w??8?OzU?>?,???e????w??8[[al?O??wbw??????????????Q?;??zW?????O????w??r?;?E???????N????zW???p???Oz??O?ywz??w??7??P9w????OSELECTsnoFROMstudentWHEREsage<>`20';SELECTsnoFROMstudentWHEREsage!z?)T20';??z-z[???????p???OzU??w??r?;?E?O??z??Nz6z-???qztSELECTsnoFROMstudentWHEREsage<`20'ORsage>`20';???a???????p???O?Y??z??v?r?;?E?v?A?4???O?????7??P9zR)Q<>)(P1)Q!z?)(??w_?O"NOT)(?I???>????zW???8?????A?O"NOT'?Ow??r???O???????8?????????r???????????ONOT?I???~?r???????y???O?r???????`????????zW???????O?g?R???p?D????NOT????P9??z`????????z?zU?????LwT?D??z????O?'z??r?D?J???m?????yw??r)QNOT'?O??w??8P9(??)???y?rWHERE?x??????z?????zWw??r?????D?????????8WHERE?x??zW????z??????A?>zt??????w??-??w?????P9??????z??????A?,?]z????8zs?????D??????w??8?O??z`wT?D???YzU??w??r?N?4????????w????O???az?wb?????????7??P9w????O-?SELECTsnoFROMstudentWHERESUB2STRING(.?O1,l)z?)T?T)V;2ZSELECTsnoFROMSCWHEREgrade/10>6;??z-z[??????????zU?????pwT?D?O??z??r???O???????=zJ?N??z-z[?????qzt:OlELECTsnoFROMstudentWHEREsnameLUCE)T?T%)V;)SELECTsnoFROMSCWHEREgrade>??;???a?O??????z????d???pwT?DP9(z4)???y?b?y?8)Q%)(?D)Qz?)(?rLIU?I???q?yzs????wy ?????b?y?8)Q%)(?D)Qz?)(?????r???????q?yzs??wy???O????zUw??r?;?E?O???a?Ywb?ywzSQL?????????p?7??P9w"?>?O???b?y?8?????r?q?yzs????z?wy?????OwT?D???Y??z??v?r?;?E???????p?7??P9w????OSELECTsnameFROMstudentWHEREsnarneLIKE)T%?J)V;?????p?7???YzU??SELECTsnameFROMstudentWHEREsnameLIKE)T?T%?J)V;?????p?7??P9(??)?????????????r?p??????zW?O?????????????????????`??????z??7??????????P9[)V]??z??????????C???p?;?E?O????z?w??r????(UNION)?????y????????P9w????OSSELECTsno?Oz?FROMstudentWHERE(sage>1SANDsdeptz?)TIS')ORsdeptz?)TCS,;???g?0?C???;?E?Ow"?>???????>??????????z[???O?'z????q???????7???Y???N???p?????2?Ow??rUNIONP9?Fz???z??Nz6???qzt:"SELECTsno,snameFROMstudentWHERE(sage>19ANDsdept=,is,)UNIONSE-LECTsno,snameFROMstudentWHEREsdept=,CSoz?P1??????SQL??????????wT?D?>?rw??????????????????y??zJ?O?b??w??rwT?D??P1?h?N?v?r?;?EP1???F????????UO?:??P1???F?????????????pP1???Fw)?1???????Z?????????????e??P9???4???<:[1]????????.???????J??????PGM].?Cz?:???Z???????`?~?O2004:485.[2]?????O?`??.?????????????N???JPGM].?Cz?:?,?z?e?????`?~?O2002:71.[3PU?Y????.SQLServer?????????r???????????>PLM].?Cz?:?t????zb???`?~?O2004:141.[4PU???v??.SQL??????wT?DPLJ].?v?5?N???????????O2003, (3).I?Hz??D?:????PFMethodsofSQLQueryRUBei(HuazhongUniversityofScienceandTechnology,Wuhan430079,China)Abstract:Atthepresenttime?OSQLoptimizationisthemainproblemsfordatabase.ThisarticleintroducesandanalysessomemethodstooptimizetheSQL,whichincludeproperindexesutilization,settingupdata,avoidingformaltransformation,etc.Thesemethodscanimprovetheefficiencyofsystem.Keywords:database;SQL;querylanguage;optimizationmethods