文档介绍：SQL语法手册Select用途:从指定表中取出指定的列的数据语法: SELECTcolumn_name(s)FROMtable_name 解释:从数据库中选取资料列,并允许从一或多个资料表中,选取一或多个资料列或资料行。SELECT陈述式的完整语法相当复杂,但主要子句可摘要为:SELECTselect_list[INTOnew_table]FROMtable_source[WHEREsearch_condition][GROUPBYgroup_by_expression][HAVINGsearch_condition][ORDERBYorder_expression[ASC|DESC]]例:“Persons”t20Stavanger选出字段名”LastName”、”FirstName”的数据SELECTLastName,FirstNameFROMPersons返回结果:LastNameFirstNameHansenOlaSvendsonTovePettersenKari选出所有字段的数据SELECT*FROMPersons返回结果: t20Stavanger   Where用途:被用来规定一种选择查询的标准语法:SELECTcolumnFROMtableWHEREcolumnconditionvalue下面的操作符能被使用在WHERE中:=,<>,>,<,>=,<=,BETWEEN,LIKE注意:在某些SQL的版本中不等号<>能被写作为!=解释:SELECT语句返回WHERE子句中条件为true的数据例:从”Persons”表中选出生活在”Sandnes”的人SELECT*FROMPersonsWHERECity='Sandnes'"Persons"表中的数据有:t20Stavanger1960返回结果:vn23Sandnes1978SvendsonStaleKaivn18Sandnes1980   And&Or用途:在WHERE子句中AND和OR被用来连接两个或者更多的条件解释:AND在结合两个布尔表达式时,只有在两个表达式都为TRUE时才传回TRUEOR在结合两个布尔表达式时,只要其中一个条件为TRUE时,OR便传回TRUE例:"Persons"表中的原始数据:vn23SandnesSvendsonStephenKaivn18Sandnes用AND运算子来查找"Persons"表中FirstName为”Tove”而且LastName为”Svendson”的数据SELECT*FROMPersonsWHEREFirstName='Tove'ANDLastName='Svendson'返回结果:vn23Sandnes用OR运算子来查找"Persons"表中FirstName为”Tove”或者LastName为”Svendson”的数据SELECT*FROMPersonsWHEREfirstname='Tove'ORlastname='Svendson'返回结果:vn23SandnesSvendsonStephenKaivn18Sandnes你也能结合AND和OR(使用括号形成复杂的表达式),如:SELECT*FROMPersonsWHERE(FirstName='Tove'ORFirstName='Stephen')ANDLastName='Svendson'返回结果:vn23SandnesSvendsonStephenKaivn18SandnesBetween…And用途:指定需返回数据的范围语法:SELECTcolumn_nameFROMtable_nameWHEREcolumn_nameBETWEENvalue1ANDvalue2例:“Persons”vn23Sandnes用BETWEEN…AND返回LastName为从”Hansen”到”Pettersen”的数据:SELECT*FROMPersonsWHERELastNameBETWEEN'Hansen'AND'Pettersen'返回结果:t20Stavanger 为了显示指定范围之外的数据,也可以用NOT操作符:SELECT*FROMPersonsWHERELastNameNOTBETWEEN'Hansen'AND'Pettersen'返回结果:vn23Sandnes  Distinct用途:DISTINCT关键字被用作返回唯一的值语法:SELECTDISTINCTcolumn-name(s)FROMtable-name解释:当column-name(s)中存在重复的值时,返回结果仅留下一个例:“Orders”pany字段中唯一的值:panySegaW3SchoolsTrio  Orderby用途:指定结果集的排序语法:SELECTcolumn-name(s)FRO