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SQL娉曞垯 PDF 涓嬭澆
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絎竴绔?鏁版嵁搴撳拰SQL
娉曞垯 1-1鍏崇郴鏁版嵁搴撲互琛屼負(fù)鍗曚綅璇誨啓鏁版嵁銆?/div>
娉曞垯 1-2涓€涓崟鍏冩牸涓彧鑳借緭鍏ヤ竴涓暟鎹€?/div>
娉曞垯 1-3瀛︿細(xì)鏍囧噯 SQL 灝卞彲浠ュ湪鍚勭 RDBMS 涓功鍐?SQL 璇彞浜嗐€?/div>
娉曞垯 1-4 SQL 鏍規(guī)嵁鍔熻兘涓嶅悓鍙互鍒嗕負(fù)涓夌被錛屽叾涓嬌鐢ㄦ渶澶氱殑鏄疍ML銆?/div>
娉曞垯 1-5 SQL 璇彞浠ュ垎鍙鳳紙; 錛夌粨灝俱€係QL 璇彞涓嶅尯鍒嗗ぇ灝忓啓SQL涓嶅尯鍒嗗叧閿?span style="white-space:pre"> 瀛楃殑澶у皬鍐?銆?/div>
娉曞垯 1-6鍏抽敭瀛椾笉鍖哄垎澶у皬鍐欍€備絾鏄彃鍏ュ埌琛ㄤ腑鐨勬暟鎹槸鍖哄垎澶у皬鍐欑殑銆?/div>
娉曞垯 1-7瀛楃涓插拰鏃ユ湡甯告暟闇€瑕佷嬌鐢ㄥ崟寮曞彿錛?#39;錛夋嫭璧鋒潵銆傛暟瀛楀父鏁版棤闇€鍔犳敞鍗?span style="white-space:pre"> 寮曞彿錛堢洿鎺ヤ功鍐欐暟瀛楀嵆鍙級銆?/div>
娉曞垯 1-8鍗曡瘝涔嬮棿闇€瑕佷嬌鐢ㄥ崐瑙掔┖鏍兼垨鑰呮崲琛岀榪涜鍒嗛殧銆?/div>
娉曞垯 1-9鏁版嵁搴撳悕縐般€佽〃鍚嶅拰鍒楀悕絳夊彲浠ヤ嬌鐢ㄤ互涓嬩笁縐嶅瓧絎︺€?/div>
鍗婅鑻辨枃瀛楁瘝
鍗婅鏁板瓧
涓嬪垝綰匡紙_錛?/div>
姝ゅ錛屽悕縐板繀欏諱互鍗婅鑻辨枃瀛楁瘝寮€澶?銆?/div>
娉曞垯 1-10鍚嶇О蹇呴』浠ュ崐瑙掕嫳鏂囧瓧姣嶄綔涓哄紑澶淬€?/div>
娉曞垯 1-11鍚嶇О涓嶈兘閲嶅銆?/div>
娉曞垯 1-12鍒犻櫎浜嗙殑琛ㄦ槸鏃犳硶鎭㈠鐨勩€傚湪鎵цDROP TABLE 璇彞涔嬪墠璇峰姟蹇呬粩緇?span style="white-space:pre"> 紜銆?/div>
娉曞垯 1-13琛ㄥ畾涔夊彉鏇翠箣鍚庢棤娉曟仮澶嶃€傚湪鎵цALTER TABLE 璇彞涔嬪墠璇峰姟蹇呬粩緇?span style="white-space:pre"> 紜銆?/div>
絎簩绔犳煡璇㈠熀紜€
娉曞垯 2-1鏄熷彿錛? 錛変唬琛ㄥ叏閮ㄥ垪鐨勬剰鎬濄€?/div>
娉曞垯 2-2璁懼畾姹夎鍒悕鏃墮渶瑕佷嬌鐢ㄥ弻寮曞彿錛?quot; 錛夋嫭璧鋒潵銆?/div>
娉曞垯 2-3鍦⊿ELECT 璇彞涓嬌鐢―ISTINCT 鍙互鍒犻櫎閲嶅琛屻€?/div>
娉曞垯 2-4 WHERE 瀛愬彞瑕佺揣璺熷湪FROM 瀛愬彞涔嬪悗銆?/div>
娉曞垯 2-5娉ㄩ噴鏄?SQL 璇彞涓敤鏉ユ爣璇嗚鏄庢垨鑰呮敞鎰忎簨欏圭殑閮ㄥ垎銆傚垎涓?琛屾敞閲?span style="white-space:pre"> 鍜屽琛屾敞閲婁袱縐嶃€?/div>
娉曞垯 2-6 SELECT 瀛愬彞涓彲浠ヤ嬌鐢ㄥ父鏁版垨鑰呰〃杈懼紡銆?/div>
娉曞垯 2-7浣跨敤姣旇緝榪愮畻絎︽椂涓€瀹氳娉ㄦ剰涓嶇瓑鍙峰拰絳夊彿鐨勪綅緗€?/div>
娉曞垯 2-8瀛楃涓茬被鍨嬬殑鏁版嵁鍘熷垯涓婃寜鐓у瓧鍏擱『搴忚繘琛屾帓搴忥紝涓嶈兘涓庢暟瀛楃殑澶у皬欏?span style="white-space:pre"> 搴忔販娣嗐€?/div>
娉曞垯 2-9甯屾湜閫夊彇NULL 璁板綍鏃訛紝闇€瑕佸湪鏉′歡琛ㄨ揪寮忎腑浣跨敤IS NULL 榪愮畻絎︺€傚笇 鏈涢€夊彇涓嶆槸NULL 鐨勮褰曟椂錛岄渶瑕佸湪鏉′歡琛ㄨ揪寮忎腑浣跨敤IS NOT NULL 榪?span style="white-space:pre"> 綆楃銆?/div>
娉曞垯 2-10 NOT 榪愮畻絎︾敤鏉ュ惁瀹氭煇涓€鏉′歡錛屼絾鏄笉鑳芥互鐢ㄣ€?/div>
娉曞垯 2-11澶氫釜鏌ヨ鏉′歡榪涜緇勫悎鏃訛紝闇€瑕佷嬌鐢ˋND 榪愮畻絎︽垨鑰匫R 榪愮畻絎︺€?/div>
娉曞垯 2-12鏂囨皬鍥懼緢鏂逛究銆?/div>
娉曞垯 2-13 AND 榪愮畻絎︾殑浼樺厛綰ч珮浜嶰R 榪愮畻絎︺€傛兂瑕佷紭鍏堟墽琛孫R 榪愮畻絎︽椂鍙?span style="white-space:pre"> 浠ヤ嬌鐢ㄦ嫭鍙楓€?/div>
娉曞垯 2-14閫氳繃鍒涘緩鐪熷€艱〃錛屾棤璁哄澶嶆潅鐨勬潯浠訛紝閮戒細(xì)鏇村鏄撶悊瑙ｃ€?/div>
絎笁绔?鑱氬悎涓庢帓搴?/div>
娉曞垯 3-1 COUNT 鍑芥暟鐨勭粨鏋滄牴鎹弬鏁扮殑涓嶅悓鑰屼笉鍚屻€侰OUNT(*) 浼?xì)寰楀埌鍖呭?span style="white-space:pre"> NULL 鐨勬暟鎹鏁幫紝鑰孋OUNT(<鍒楀悕>) 浼?xì)寰楀埌NULL 涔嬪鐨勬暟鎹鏁般€?/div>
娉曞垯 3-2鑱氬悎鍑芥暟浼?xì)灏哊ULL 鎺掗櫎鍦ㄥ銆備絾COUNT(*) 渚嬪錛屽茍涓嶄細(xì)鎺掗櫎NULL 銆?/div>
娉曞垯 3-3 MAX/MIN 鍑芥暟鍑犱箮閫傜敤浜庢墍鏈夋暟鎹被鍨嬬殑鍒椼€係UM/AVG 鍑芥暟鍙€傜敤 浜庢暟鍊肩被鍨嬬殑鍒椼€?/div>
娉曞垯 3-4鎯寵璁＄畻鍊肩殑縐嶇被鏃訛紝鍙互鍦–OUNT 鍑芥暟鐨勫弬鏁頒腑浣跨敤DISTINCT 銆?/div>
涓嶄粎闄愪簬 COUNT 鍑芥暟錛屾墍鏈夌殑鑱氬悎鍑芥暟閮藉彲浠ヤ嬌鐢?DISTINCT 銆?/div>
娉曞垯 3-5鍦ㄨ仛鍚堝嚱鏁扮殑鍙傛暟涓嬌鐢―ISTINCT 錛屽彲浠ュ垹闄ら噸澶嶆暟鎹€?/div>
娉曞垯 3-6 GROUP BY 灝卞儚鏄垏鍒嗚〃鐨勪竴鎶婂垁銆傛澶栵紝GROUP BY 瀛愬彞鐨勪功鍐欎綅緗?span style="white-space:pre"> 涔熸湁涓ユ牸瑕佹眰錛屼竴瀹氳鍐欏湪 FROM 璇彞涔嬪悗錛堝鏋滄湁 WHERE 瀛愬彞鐨?span style="white-space:pre"> 璇濋渶瑕佸啓鍦?WHERE 瀛愬彞涔嬪悗錛夈€?/div>
娉曞垯 3-7 SQL 瀛愬彞鐨勯『搴忎笉鑳芥敼鍙橈紝涔熶笉鑳戒簰鐩告浛鎹€?/div>
娉曞垯 3-8鑱氬悎閿腑鍖呭惈NULL 鏃訛紝鍦ㄧ粨鏋滀腑浼?xì)浠?ldquo;涓嶇‘瀹?rdquo;琛岋紙絀鴻錛夌殑褰㈠紡琛ㄧ幇 鍑烘潵銆?/div>
娉曞垯 3-9浣跨敤GROUP BY 瀛愬彞鏃訛紝SELECT 瀛愬彞涓笉鑳藉嚭鐜拌仛鍚堥敭涔嬪鐨勫垪鍚嶃€?/div>
娉曞垯 3-10鍦℅ROUP BY 瀛愬彞涓笉鑳戒嬌鐢⊿ELECT 瀛愬彞涓畾涔夌殑鍒悕銆?/div>
娉曞垯 3-11 GROUP BY 瀛愬彞緇撴灉鐨勬樉紺烘槸鏃犲簭鐨勩€?/div>
娉曞垯 3-12鍙湁SELECT 瀛愬彞鍜孒AVING 瀛愬彞錛堜互鍙?qiáng)ORDER BY 瀛愬彞錛変腑鑳藉浣跨敤 鑱氬悎鍑芥暟銆?/div>
娉曞垯 3-13 HAVING 瀛愬彞瑕佸啓鍦℅ROUP BY 瀛愬彞涔嬪悗銆?/div>
娉曞垯 3-14鑱氬悎閿墍瀵瑰簲鐨勬潯浠朵笉搴旇涔﹀啓鍦℉AVING 瀛愬彞褰撲腑錛岃€屽簲璇ヤ功鍐欏湪 WHERE 瀛愬彞褰撲腑銆?/div>
娉曞垯 3-15 ORDER BY 瀛愬彞閫氬父鍐欏湪SELECT 璇彞鐨勬湯灝俱€?/div>
娉曞垯 3-16鏈寚瀹歄RDER BY 瀛愬彞涓帓鍒楅『搴忔椂浼?xì)榛樿鋴社敤鍗囧簭杩涜鎺掑垪銆?/div>
鐢變簬 ASC 鍜?DESC 榪欎袱涓叧閿瓧鏄互鍒椾負(fù)鍗曚綅鎸囧畾鐨勶紝鍥犳鍙互鍚?span style="white-space:pre"> 鏃舵寚瀹氫竴涓垪涓哄崌搴忥紝鎸囧畾鍏朵粬鍒椾負(fù)闄嶅簭銆?/div>
娉曞垯 3-17鎺掑簭閿腑鍖呭惈NULL 鏃訛紝浼?xì)鍦ㄥ紑澶存垨鏈熬榪涜姹囨€匯€?/div>
娉曞垯 3-18鍦?ORDER BY 瀛愬彞涓彲浠ヤ嬌鐢⊿ELECT 瀛愬彞涓畾涔夌殑鍒悕銆?/div>
娉曞垯 3-19鍦∣RDER BY 瀛愬彞涓彲浠ヤ嬌鐢⊿ELECT 瀛愬彞涓湭浣跨敤鐨勫垪鍜岃仛鍚堝嚱鏁般€?/div>
娉曞垯 3-20鍦∣RDER BY 瀛愬彞涓笉瑕佷嬌鐢ㄥ垪緙栧彿銆?br />
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