Ulimi Lokusebenza Oluhlelekile (SQL) yisethi yemiyalelo esetshenziselwa ukusebenzisana nedatha yokuxhumana . Eqinisweni, i-SQL yilona ulimi olulodwa ulwazi olubanzi oluqondayo. Noma nini lapho uxhumana ne-database enjalo, isofthiwe ihumusha imiyalo yakho (kungakhathaliseki ukuthi ukuchofoza kwegundane noma ukufakelwa kwefomu) kwisitatimende se-SQL ukuthi i-database ikwazi ukuyihumusha. I-SQL inezingxenye ezintathu eziyinhloko: Ulimi Lokusetshenziswa Kokudatha (DML), uLimi LokuDluliswa KweDatha (DDL), noLimi Lokulawula Ukwaziswa (DCL).
Ukusetshenziswa Okuvamile kwe-SQL kuwebhu
Njengomsebenzisi kunoma yiluphi uhlelo lwesofthiwe olushicilelwe phansi, cishe usebenzisa i-SQL, noma ngabe awukwazi. Isibonelo, ikhasi lewebhu elinamandla elinamakhasimende (njengamawebhusayithi amaningi) lithatha okufakwayo komsebenzisi kusuka kumafomu nokuchofoza bese ulisebenzisa ukuze kubhale umbuzo we-SQL othola ulwazi oluvela kulwazi oludingekayo ukudala ikhasi lewebhu elilandelayo.
Cabanga ngesibonelo se-catalog elula e-intanethi enomsebenzi wokusesha. Ikhasi lokusesha lingase liqukethe ifomu eliqukethe ibhokisi lombhalo lapho ufaka khona isikhathi sokusesha bese uchofoza inkinobho yokusesha. Uma uchofoza inkinobho, iseva yewebhu ithola noma yimaphi amarekhodi kusuka ku-database yomkhiqizo equkethe igama lokusesha futhi isebenzisa imiphumela ukudala ikhasi lewebhu eliqondene nesicelo sakho.
Isibonelo, uma usesha imikhiqizo equkethe igama elithi "i-Irish," iseva ingasebenzisa isitatimende esilandelayo se-SQL ukuze ithole imikhiqizo ehlobene:
Kuhunyushwe, lo myalo uthola noma yikuphi amarekhodi avela kuthebula lemininingwane ebizwa ngokuthi "imikhiqizo" equkethe izinhlamvu "zishaya" noma kuphi ngaphakathi kwegama lomkhiqizo.
Ulimi Lokusebenzisa Ukudatha
Ulimi Lokusetshenziswa Kwedatha (i-DML) luqukethe i-subset yemilayezo ye-SQL esetshenziselwa kakhulu - leyo elula ukusebenzisa okuqukethwe kwedatha ngenye indlela. Imiyalo emine ejwayelekile kunazo zonke ze-DML ithola ulwazi oluvela kumyalelo wedatha (i-SELECT), engeza ulwazi olusha ku-database (umyalo we-INSERT), lungisa imininingwane okwamanje egciniwe ku-database (umyalo we-UPDATE), futhi ususe ulwazi kusuka ku-database ( Sula umyalo).
Ulimi lokuchazwa kwedatha
Ulimi Lokuchaza Idatha (DDL) liqukethe imiyalo engasetshenziswa kakhulu. Imiyalo ye-DDL ishintsha isakhiwo sangempela se-database, kunokuqukethwe okuqukethwe kwedatha. Izibonelo zomyalo weDDL ovame ukusetshenziswa zihlanganisa lezo ezisetshenziselwa ukukhiqiza ithebula lemininingwane elisha (DALA ITHEBULA), shintsha isakhiwo setafula lemininingwane (ALTER TABLE), futhi ususe ithebula lemininingwane (DROP TABLE).
Ulimi Lokulawula Idatha
Ulimi Lokulawula Idatha (DCL) lisetshenziselwa ukuphatha ukufinyelela komsebenzisi kuma-yolwazi . Iqukethe imiyalo emibili: umyalo woku-GRANT, osetshenziselwa ukwengeza izimvume zesistimu zomsebenzisi, nomyalo we-REVOKE, osetshenziselwa ukususa izimvume ezikhona. Le miyalo emibili yakha umgogodla wesibonelo sokuvikela database.
Isakhiwo somyalo we-SQL
Ngenhlanhla kulabo abangekho uhlelo lwekhompiyutha, imiyalo ye-SQL yenzelwe ukuba ne-syntax efana nesiNgisi. Ngokuvamile ziqala ngesitatimende somyalo esichaza isenzo okufanele sithathe, kulandelwa isigatshana esichaza umgomo womyalo (njengetafula elithile ngaphakathi kwedatha ethintekayo ngumyalo) futhi ekugcineni, uchungechunge lwezigaba ezinikeza imiyalelo eyengeziwe.
Ngokuvamile, ukufunda isitatimende se-SQL ngokuzwakalayo kuzokunika umqondo omuhle kakhulu walokho umyalo okuhloswe ukukwenza. Thatha isikhashana ukufunda lesi sibonelo sesitatimende se-SQL:
Ungacabanga ukuthi lesi sitatimende sizokwenzani? It ukufinyelela itafula umfundi umfundi futhi ususe wonke amarekhodi abafundi abaphothula ngo-2014.
Ukufunda i-SQL Programming
Sibheke izibonelo ezimbalwa ze-SQL ezilula kule ngqikithi, kepha i-SQL ulimi olubanzi nolunamandla. Ukuze uthole isingeniso esengeziwe ngokujulile, bheka Okusemqoka kwe-SQL .