下面的例子是一個(gè)名為"s"的表 Oxford 2FifthNew Changan SQL下面的語(yǔ)句從表中選取LastName列的數(shù)據(jù)：SELECTLastNameFROM SQLDMLSQLDML)DDLSQLSQLSQLDMLSELECTINSERTINTOSQLDDLCREATEDATABASEALTERDATABASECREATETABLEALTERTABLE（改變）DROPTABLECREATEINDEX（搜索鍵DROPINDEXSQLSELECT在一個(gè)結(jié)果表中（稱(chēng)為結(jié)果集）SQLSELECTSELECTSELECTFROM以及 SELECT*SELECT*FROM注釋?zhuān)篠QLSELECTselectSQLSELECTSELECTSELECTLastName,FirstName s"表 1Oxford2FifthNew3Changan結(jié)果 SQLSQLSELECT**SELECTSELECT* 1Oxford2FifthNew3ChanganSQLSQLSELECTDISTINCTSELECTDISTINCTSELECTDISTINCTFROM FROM結(jié)果 SELECT FROM結(jié)果 SELECTSELECTFROMWHERE下面的運(yùn)算符可在WHERE子句中使用 =><使用WHERE子句"Beijing"SELECTWHERESELECT* sWHERE"s"OxfordFifthNewChanganXuanwumenChanganXuanwumenSELECT*sWHERESELECT*sWHERE數(shù)值 SELECT*sWHERESELECT*sWHEREANDOR原始的表(用在例子中的)： OxfordFifthNewChanganXuanwumenAND"Carter"Thomas" 結(jié)果 ChanganOROROR"Carter"Thomas" ChanganXuanwumenANDORANDOR（使用圓括號(hào)來(lái)組成復(fù)雜的表達(dá)式 AND結(jié)果 ChanganXuanwumenORDERBY原始的表(用在例子中的)：Orders ,OrderNumberFROMOrdersORDER實(shí)例 ,OrderNumberFROMOrdersORDER,,OrderNumberFROMOrdersORDER實(shí)例 以逆字母順序顯示公司名稱(chēng)，并以數(shù)字順序顯示順序號(hào) ,OrderNumberFROMOrdersORDERDESC,OrderNumber結(jié)果 同的值時(shí)，第二列是以升序排列的。如果第一列中有些值為nulls時(shí)，情況也是這樣的。INSERTINTOINSERTINSERTINTOVALUES12,.)"s""s"INSERTINSERTINTOtable_name12,VALUES12,.ChanganSQLSQLINSERTINSERT sVALUES('Gates','Bill','Xuanwumen10', ChanganXuanwumen"s"表 ChanganXuanwumenSQLSQLINSERTINSERTs(LastName,Address)VALUES('Wilson', ChanganXuanwumenChamps-SQLOrder SQL SQL測(cè) UpdateUpdate XuanwumenChamps-lastname"Wilson" SETFirstName='Fred'WHERELastName=結(jié)果 XuanwumenChamps- SETAddress='Zhongshan23',City=WHEREWHERELastName= XuanwumenDELETEDELETEDELETEDELETEFROMWHERE Xuanwumen"Fred"FredWilson"DELETE WHERELastName=結(jié)果 XuanwumenDELETEDELETEFROM或者 DELETEDELETE*FROMTOPSQLServerSELECTSELECTTOPnumber|percentcolumn_name(s)FROMtable_nameMySQLMySQLOracleSQLSELECTTOPMySQLFROMtable_nameLIMITnumberSELECTSELECTLIMIT5sOracle語(yǔ) FROMtable_nameWHEREROWNUM<=SELECTsSELECTsWHEREROWNUM<=s1Oxford2FifthNew3Changan4PennsylvaniaSQLSQLTOPSELECTTOP2* 結(jié)果 1Oxford2FifthNewSQLTOPSQLTOPPERCENTs50%SELECTTOP50PERCENT* 1Oxford2FifthLIKESQLLIKEFROMtable_nameWHEREcolumn_nameLIKEs1Oxford2FifthNew3ChanganLIKELIKEs"NSELECT*FROM WHERECityLIKE'N%'2FifthNews""g"SELECT*FROM WHERECityLIKE'%g'3Changans""lon"我們可以使用下面的SELECT語(yǔ)句 SELECTSELECT*sWHERECityLIKE結(jié)果集 1Oxford通過(guò)使用NOTs""lon"SELECT*sWHERECityNOTLIKE結(jié)果集 2FifthNew3Changan通配通配 描%_s1Oxford2FifthNew3ChanganSELECT*sWHERECityLIKE 2FifthNewSELECTSELECT*sWHERECityLIKE 1Oxford__SELECT*sWHEREFirstNameLIKE 2FifthNews"表中選取的這條記錄的姓氏以"C""rSELECT* WHEREWHERELastNameLIKE 3Changan[charlist]s"A""L""NSELECTSELECT*sWHERECityLIKE 1Oxford2FifthNewSELECTSELECT*sWHERECityLIKE結(jié)果集 3ChanganINININWHERESQLINFROMtable_nameWHEREcolumn_nameINs1Oxford2FifthNew3ChanganININAdamsCarterSELECT*sWHERELastNameIN 1Oxford3ChanganBETWEENBETWEENWHEREBETWEENSQLBETWEENFROMtable_nameWHEREcolumn_nameBETWEENvalue1ANDs1Oxford2FifthNew3Changan4Xuanwumen的SQL：SELECT*WHEREsBETWEENBETWEEN'Adams'AND 1Oxford2FifthNew重要事項(xiàng)：不同的數(shù)據(jù)庫(kù)對(duì)BETWEEN...AND操作符的處理方式是有差異的。某些數(shù)據(jù)庫(kù)會(huì)列出介于"Adams"和"Carter"之間的人，但不包括"Adams"和"Carter"；某些數(shù)據(jù)庫(kù)會(huì)列出介于"Adams"和"Carter"之間并包括"Adams"和"Carter"的人；而另一些數(shù)據(jù)庫(kù)會(huì)列出介于"Adams"和"Carter"之間的人，包括"Adams"，但不包括"Carter"。BETWEEN.ANDSELECTSELECT*WHEREsNOTBETWEEN'Adams'AND 3Changan4XuanwumenSQL，可以為列名稱(chēng)和表名稱(chēng)指定別名（Alias）。SQLAliasSQLAliasSELECT表FROMFROMASSELECTcolumn_nameASalias_nameFROMtable_nameAlias實(shí)例SELECTcolumn_nameASalias_nameFROMtable_nameAlias實(shí)例和"po"。"和JohnAdams"SELECTpo.OrderID,p.LastName,sASp,Product_OrdersASWHEREp.LastName='Adams'AND不使用別名的SELECT語(yǔ)句 s,s.LastName='Adams'1Oxford2FifthNew3ChanganSELECTLastNameSELECTLastNameASFamily,FirstNameASs結(jié)果 SQLSQLjoinJoinjoin中的所有數(shù)據(jù)的情況下，把表間的數(shù)據(jù)交叉在一起。1Oxford2FifthNew3Changan使兩個(gè)人的完全相同，Id_P也可以區(qū)分他們。"Orders" 132331415請(qǐng)注意，"Id_O"列是請(qǐng)注意，"Id_O"列是Orders，"Orders"表中的"Id_P" s,s.FirstName,s.Id_P=結(jié)果集 SQLSQLJOINss.FirstName,INNERJOIN s.Id_P=Orders.Id_PORDERBY SQLSQLSQLSQLINNERJOIN在表中存在至少一個(gè)匹配時(shí)，INNERJOININNERJOINSELECTSELECTFROMINNERJOINON注釋?zhuān)篒NNER注釋?zhuān)篒NNERJOINJOIN""s" Oxford2FifthNew3Changan 13233141 SELECTs.FirstName,SELECTs.FirstName,sINNERJOIN ORDER 結(jié)果集 SQLLEFTJOINs"LEFTJOIN關(guān)鍵字會(huì)從左表(table_name1)SELECTFROMLEFTSELECTFROMLEFTLEFTJOINON注釋?zhuān)鹤⑨專(zhuān)篖EFTJOINLEFTOUTERJOIN"Orders"Changan3NewFifth2Oxford1 s"132331415左連接（LEFT左連接（LEFTJOIN）s.FirstName,sLEFTJOIN ORDER 結(jié)果集 LEFTLEFTJOIN關(guān)鍵字會(huì)從左表 s)那里返回所有的行，即使在右表SQLRIGHTJOINRIGHTJOIN關(guān)鍵字會(huì)右表(table_name2)那里返回所有的行，即使在左表RIGHTJOIN關(guān)鍵字語(yǔ) SELECTSELECTFROMRIGHTJOINON注釋?zhuān)涸谀承?shù)據(jù)庫(kù)中，RIGHTJOIN稱(chēng)為RIGHTOUTERJOIN s"1Oxford2FifthNew3Changan"Orders""Orders"132331415右連接（右連接（RIGHTJOIN）s.FirstName,sRIGHTJOIN ORDER SQLFULLJOIN只要其中某個(gè)表存在匹配，F(xiàn)ULLJOINSELECTFROMFULLSELECTFROMFULLJOINON注釋?zhuān)涸谀承?shù)據(jù)庫(kù)中，F(xiàn)ULLJOIN稱(chēng)為FULLOUTERJOIN s" Oxford 2FifthNew Changan "Orders"表 23 41 SELECTs.FirstName,SELECTs.FirstName,sFULLJOIN ORDER 結(jié)果集 FULLFULLJOINsOrders s"中的行在表"Orders"中沒(méi)有匹配，或者如果"Orders"中的行在表 s"SQLUNION的數(shù)據(jù)類(lèi)型。同時(shí)，每條SELECT語(yǔ)句中的列的順序必須相同。SELECTcolumn_name(s)FROMSELECTSELECTcolumn_name(s)FROMSELECTcolumn_name(s)FROMSELECTcolumn_name(s)FROMUNIONSELECTcolumn_name(s)SELECTcolumn_name(s)FROMUNIONSELECTcolumn_name(s)FROM另外，UNIONUNIONSELECTWang,Zhang, : Carter,Yang, Adams, Bush, Carter,Gates,UNIONUNION和SELECTE_NameFROMSELECTE_NameFROM結(jié) Zhang, Wang,Carter,Yang,Gates,Gates, Bush,Adams, 和名字相同的雇員，他們當(dāng)中只有一個(gè)人被列出來(lái)了。UNION命令只會(huì)選取不同的SQLStatementUNIONSQLStatementUNIONALL列 的所有的雇員SELECTE_NameFROMUNIONSELECTE_NameFROM結(jié) Zhang, Wang,Carter,Yang,Adams, Bush,Carter,Gates,SQLSQLSELECTINTOSELECTINTOSQLSELECTINTOSELECTINTOnew_table_name[INexternaldatabase]FROMold_tablename或者只把希望的列插入新表 SELECTSELECTINTOnew_table_name[INexternaldatabase]FROMold_tablenameSELECTSQLSELECTINTO下面的例子會(huì)制作 ssIN子句可用于向另一個(gè)數(shù)據(jù)庫(kù)中拷貝表 SELECTSELECTsINs如果我們希望拷貝某些域，可以在SELECT語(yǔ)句后列出這些域 sSQLSELECTINTOWHEREWHERE列的名為 s_backup"的表sWHERESQLSELECTINTOsINNERINNERJOINALTERALTERTABLESQLALTERTABLEALTERTABLEtable_nameALTERTABLEtable_nameALTERTABLEtable_name注釋?zhuān)耗承?shù)據(jù)庫(kù)系統(tǒng)不允許這種在數(shù)據(jù)庫(kù)表中刪除列的方式(DROPCOLUMNALTERTABLEALTERCOLUMNcolumn_names1Oxford請(qǐng)注意，新列"Birthday"請(qǐng)注意，新列"Birthday"dateALTERsALTERCOLUMNBirthday現(xiàn)在我們希望改變 s"表中"Birthday"列的數(shù)據(jù)類(lèi)型SQL ADDBirthdaySQLALTERTABLE s"中添加一個(gè)名為"Birthday"的新列SQL2FifthNew3Changan1Oxford2Fifth3請(qǐng)注意，"Birthday"請(qǐng)注意，"Birthday"year，24DROPDROPCOLUMNALTERALTERs1Oxford2FifthNew3ChanganSQLMySQLDateDATEDATEDATESQLServerDate SQLDateDATEYYYY-MM-DATETIMEYYYY-MM-DDTIMESTAMPYYYY-MM-DDYEARYYYYDATEYYYY-MM-DATETIMEYYYY-MM-DDSQL"Orders" 1234為為SELECT*FROMOrdersWHEREOrderDate='2008-12-結(jié)果集 13現(xiàn)在假設(shè)"Orders"類(lèi)似這樣（請(qǐng)注意"OrderDate"列中的時(shí)間部分 12008-12-2622008-12-2632008-11-1242008-10-19如果我們使用上面的SELECT語(yǔ)句 SELECTSELECT*FROMOrdersWHEREOrderDate='2008-12- NULLISNULLISNOTNULLSQLNULL的記錄。這意味著該字段將以NULL值保存。注釋?zhuān)篘ULL0；SQLNULL請(qǐng)看下面的 s"表12FifthNew3帶值的記錄，"Address"NULL須使用ISNULL和ISNOTNULL操作符。SQLISISNULLWHEREAddressISs 提示：ISNULLNULLSQLISNOT"Address"NULLISNOTNULLWHEREAddressISNOTs Fifth和"Products"123FROMProducts"UnitsOnOrder"NULL，NULL。微軟的ISNULL()函數(shù)用于規(guī)定如何處理NULL值。在這里，我們希望NULL值為0。"UnitsOnOrder"NULLNULL返回0SQLServer/MSFROMProductsOracleOracleISNULL()NVLSELECTFROMFROMMySQLMySQLISNULL()ISNULL()MySQLIFNULL(FROMProducts或者我們可以使用COALESCE()函數(shù)，就像這樣 FROMProductsAccess、MySQLSQLServerAccess 0255132,76832,7672允許介于-2,147,483,648與4481548通常從1開(kāi)始。48或TrueFalse（注釋?zhuān)篩es/NoNull1Ole可以 、音頻、或其他BLOBs(BinaryLargeOBjects) 4MySQLMySQLText 符）255用 BLOBs(BinaryLargeOBjects)。存放最用 BLOBs(BinaryLargeOBjects)。存放最Number -1281270255*。在括號(hào)中規(guī)定 常規(guī)。0 *UNSIGNED。通常，整數(shù)可以是負(fù)數(shù)或正數(shù)。如果添加UNSIGNED屬性，那么范圍將從0開(kāi)始，而不是某個(gè)負(fù)數(shù)。Date**DATETIMETIMESTAMPINSERTUPDATETIMESTAMPTIMESTAMP接受不同的格式，比如YYYYMMDDHHMMSS、YYMMDDHHMMSS、YYYYMMDD或SQLServer'1000-01-019999-12-*日期和時(shí)間的組合。格式：YYYY-MM-DD'1000-01-0100:00:00'12-31*時(shí)間戳。TIMESTAMP值使用Unix('1970-01-01注釋?zhuān)褐С值姆秶菑?1970-01-0100:00:01'UTC到'2038-01-0903:14:07'時(shí)間。格式：HH:MM:SS注釋?zhuān)褐С值姆秶菑?-838:59:59'到'838:59:59'24許的值：70到69，表示從1970到2069。 nBinaryBinaryUnicode存 Unicode4,000Unicode4,000Unicode536,870,912Unicode2GB 0、1存存Number儲(chǔ)025532,76832,7672,147,483,6482,147,483,647允許介于 和固定精度和比例的數(shù)字。允許從-10^38+1到10^381p參數(shù)指示可以的最大位數(shù)（小數(shù)點(diǎn)左側(cè)和右側(cè)）。p必須是1到38之間的值。默認(rèn)是18。s參數(shù)指示小數(shù)點(diǎn)右側(cè)的最大位數(shù)。s必須是p0固定精度和比例的數(shù)字。允許從-10^38+1到10^381p參數(shù)指示可以的最大位數(shù)（小數(shù)點(diǎn)左側(cè)和右側(cè)）。p必須是1到38之間的值。默認(rèn)是18。s參數(shù)指示小數(shù)點(diǎn)右側(cè)的最大位數(shù)。s必須是p0介于-214,748.3648和214,748.3647 -和8節(jié)1.79E3081.79E308據(jù)。參數(shù)n指示該字段保存4字節(jié)還是8字節(jié)。float(24)4float(538n的默認(rèn)值是53。43.40E383.40E38Date 175311999912313.33817531199991231100 日到 月6日，精度為1分鐘。4僅日期。從0001年1月1日到999912313僅時(shí)間。精度為100納秒字會(huì)更新。timestamp真實(shí)時(shí)間。每個(gè)表只能有一個(gè)timestamp變ntext以及timestamp。(GUID)XML2GB。。SQLSELECTfunctionSELECTfunctionFROMAggregateScalar合計(jì)函數(shù)（Aggregate注釋?zhuān)喝绻赟ELECT語(yǔ)句的項(xiàng)目列表中的眾多其它表達(dá)式中使用SELECTSELECTGROUPBY""s"table(在大部分的例子中使用過(guò) Adams,Bush,Carter,MSAccess中的合計(jì)函 返回某列的行數(shù)（不包括NULL值SQLServer 返回某列的行數(shù)（NULLScalarScalarMSAccessScalarSQLAVGSELECTSELECTAVG(column_name)FROMSQLAVG()"Orders 123456SQLSELECTAVG(OrderPrice)ASOrderAverageFROMOrderPriceOrderPriceSQLSELECTCustomerFROMWHEREOrderPrice>(SELECTAVG(OrderPrice)FROM結(jié)果集類(lèi)似這樣 SQLCOUNT)SELECTCOUNT(column_name)SELECTCOUNT(column_name)FROMSQLCOUNT(*)SELECTCOUNT(*)FROMSQLCOUNT(DISTINCTcolumn_nameSELECTSELECTCOUNT(DISTINCTcolumn_name)FROM注釋?zhuān)篊OUNT(DISTINCT)適用于ORACLE和SQLServer，但是無(wú)法用于Access。SQLCOUNT(column_name"Orders" 123456SELECTCOUNT(Customer)ASCustomerNilsenFROMOrdersWHERECustomer='Carter'SQL語(yǔ)句的結(jié)果是2，Carter22SQLSQLCOUNT(*WHERE"Orders"（Bush,CarterAdams）SQLFIRSTSELECTSELECTCOUNT(*)ASNumberOfOrdersFROMSQLCOUNT(DISTINCTSQLCOUNT(DISTINCTcolumn_name6SELECTSELECTCOUNT(DISTINCTCustomer)ASNumberOfCustomersFROM 3SELECTSELECTFIRST(column_name)FROMSQLFIRST"Orders123456SQLSELECTFIRST(OrderPrice)ASFirstOrderPriceFROM結(jié)果集類(lèi)似這樣 SQLSQLSQL測(cè) LASTLAST提示：ORDERBYSQLLASTSELECTSELECTLAST(column_name)FROMSQLLAST"Orders 123456SELECTLAST(OrderPrice)ASLastOrderPriceFROM結(jié)果集類(lèi)似這樣 MAXMAXSQLMAXSELECTSELECTMAX(column_name)FROMSQLMAX"Orders 123456SELECTMAX(OrderPrice)ASLargestOrderPriceFROM結(jié)果集類(lèi)似這樣 MINMINSQLMINSELECTSELECTMIN(column_name)FROMSQLMIN"Orders 123456SELECTMIN(OrderPrice)ASSmallestOrderPriceFROM結(jié)果集類(lèi)似這樣 SUM()SUM()SQLSUM(SELECTSELECTSUM(column_name)FROMGROUPGROUPBYSQLGROUPBYFROMtable_nameWHEREcolumn_nameoperatorvalueGROUPBYcolumn_nameSQLSQLGROUPBY"Orders123456我們想要使用GROUPBY語(yǔ)句對(duì)客戶(hù)進(jìn)行組合。SELECTCustomer,SUM(OrderPrice)FROMGROUPGROUPBY GROUPBYSELECTSELECTCustomer,SUM(OrderPrice)FROM結(jié)果集類(lèi)似這樣 那么為什么不能使用上面這條SELECT語(yǔ)句呢？解釋如下：上面的SELECT語(yǔ)句指定了兩列（Customer SUM(OrderPrice)）。"SUM(OrderPrice)"返回一個(gè)單獨(dú)的（"OrderPrice"列的總計(jì)），而"Customer"返回6個(gè)值（每個(gè)值對(duì)應(yīng)"Orders"表中的每一行）。因此，我們得不到正確的結(jié)果。不過(guò)，您已經(jīng)看到了，GROUP（"OrderPrice"列的總計(jì)），而"Customer"返回6個(gè)值（每個(gè)值對(duì)應(yīng)"Orders"表中的每一行）。因此，我們得不到正確的結(jié)果。不過(guò)，您已經(jīng)看到了，GROUPBY語(yǔ)句解決了SELECTSELECTCustomer,OrderDate,SUM(OrderPrice)FROMOrdersGROUPBYCustomer,OrderDateSQLSUM"Orders123456SELECTSUM(OrderPrice)ASOrderTotalFROM結(jié)果集類(lèi)似這樣 SUMGROUPBYHAVINGSQLHAVINGWHERESQLHAVINGFROMtable_nameWHEREcolumn_nameoperatorvalueGROUPBYcolumn_nameHAVINGaggregate_function(column_name)operatorSQLSQLHAVING"Orders123456SQLSQLUCASE()Bush"Adams"1500SQLWHERE我們使用如下SQL語(yǔ)句 SELECTSELECTCustomer,SUM(OrderPrice)FROMOrdersGROUPBYCustomerHAVING結(jié)果集類(lèi)似 SELECTSELECTCustomer,SUM(OrderPrice)FROMOrdersWHERECustomer='Bush'ORCustomer='Adams'GROUPBYCustomerHAVING結(jié)果集 UCASE()UCASE()SELECTUCASE(column_name)FROMSQLUCASE()我們擁有下面這個(gè)"s"表 1Oxford2FifthNew3ChanganSQLSELECTUCASE(LastName)asLastName,FirstName 結(jié)果集類(lèi)似這樣 LCASE()LCASE()SQLLCASESELECTLCASE(column_name)FROMSQLLCASEs"1Oxford2FifthNew3ChanganSQLSELECTLCASE(LastName)asLastName,FirstName 結(jié)果集類(lèi)似這樣 MID(SQLMIDSELECTSELECTMID(column_name,start[,length])FROM 必需。規(guī)定開(kāi)始位置（1）SQLMID我們擁有下面這個(gè)"s"表 1Oxford2FifthNew3Changan"City""City"3SELECTMID(City,1,3)asSmallCity LEN()LEN()SQLLEN()SELECTSELECTLEN(column_name)FROMSQLLEN()我們擁有下面這個(gè)"s"表 1Oxford2FifthNew3ChanganSELECTLEN(City)asLengthOfCity 結(jié)果集類(lèi)似這樣 687ROUNDROUNDSQLROUND()SELECTROUND(column_name,decimals)FROM SQLROUND()"Products 110002100031000SELECTProductName,ROUND(UnitPrice,0)asUnitPriceFROM結(jié)果集類(lèi)似這樣 7NOWNOWSELECTNOW()FROMSQLSELECTNOW()FROMSQLNOW"Products 1100