Ukudala iDatabase
Ngaba ulungele ukuqala ukudala iinkcukacha kunye neetafile ngeLwimi loCwangciso oluCwangcisiweyo ? Kule nqaku, sihlolisisa inkqubo yokudala amatafula ngesandla kunye ne- CREATE DATABASE kunye ne-CREATE TABLE. Ukuba untsha ku-SQL, unokuba unqwenela ukuphonononga i- SQL ye-Basics kwinqaku yokuqala.
Iimfuno zoshishino
Ngaphambi kokuba sihlale kwibhodibhodi, kufuneka siqinisekise ukuba sinokuqonda okucacileyo iimfuno zabaxhasi. Iyiphi indlela engcono yokufumana le ngqiqo? Ukuthetha nomthengi, kunjalo! Emva kokuhlala phantsi kunye noMlawuli wezoLuntu we-XYZ, sifunde ukuba yinkampani yokuthengisa iwijethi kwaye ngokuyinene inomdla ekulandeleni ulwazi kubasebenzi babo bokuthengisa.
I-XYZ idibanisa i-force force yayo yokuthengisa kwimimandla esempuma nasentshonalanga, nganye leyo eyahlula kwimimandla eninzi efunyenwe yi-reps yokuthengisa. ISebe le-HR lingathanda ukulandelela ummandla owenziwe ngumqeshwa ngamnye kunye nolwazi lomvuzo ngamnye lomqeshwa kunye nesakhiwo solawulo. Ukuze sihlangabezane nale mfuno, senze i-database elineetable ezintathu, eziboniswe kwisichazo sobudlelwane beCandelo kule phepha.
Ukukhetha iSipatform Database
Sinqume ukusebenzisa inkqubo yolawulo lweenkcukacha (okanye i-DBMS) eyakhiwe kwiLwimi yoCwangciso oluCwangcisiweyo (SQL). Ngoko ke, yonke imigaqo yedatha kunye nemithetho yokudala itafile kufuneka ibhalwe phantsi nge-ANSI SQL engqondweni.
Njengenzuzo eyongeziweyo, usebenzisa i-ANQ-Compliance SQL iya kuqinisekisa ukuba le miyalelo iza kusebenza nakuphi na iDBMS exhasa iS standard Standard , kuquka i-Oracle kunye ne-Microsoft SQL Server. Ukuba awukhe ukhetha iqonga lakho ledatha ngoku, i-article ye- Database Database Options ikuhamba kwinkqubo yokukhetha.
Ukudala iDatabase
Isinyathelo sethu sokuqala kukudala idata ngokwalo. Iinkqubo ezininzi zolawulo lweenkcukacha zinikezela uluhlu lwezinto ezikhethiweyo ukwenza ukulungiswa kwemimiselo ye-database kwili nyathelo, kodwa i-database yethu ivumela kuphela ukudala ukudala kwedatha. Njengoko kunye nayo yonke imiyalelo yethu, unokunqwenela ukubonisana namaxwebhu kwi-DBMS yakho ukuqinisekisa ukuba ngaba nayiphi na iipameters eziphambili ezixhaswa yinkqubo yakho ethile zihlangabezana neemfuno zakho. Makhe sisebenzise umyalelo we-CREATE DATABASE ukuseka isiseko sethu:
DALA abasebenzi baseDATABASE Thatha inqaku elikhethekileyo lemali esetyenzisiweyo kumzekelo ongentla. Kuyinto eqhelekileyo phakathi kwabasebenzisi beSQL ukusebenzisa zonke iibrari ezinkulu ze-SQL amagama angundoqo anjenge- "CREATE" kunye ne "DATABASE" ngelixa usebenzisa zonke ii-letters ezincinci ngamagama achazwe ngumsebenzisi njengegama elithi "abasebenzi" ledatha. Ezi ndibano zibonelela ngokulula ukufunda.
Qhubeka ufunda le tutorial njengoko senza amatafula kwiziko lethu.
UkuFunda okungakumbi
Ukuba ungathanda ukufunda ngokubanzi ngeeLwimi eziCwangcisiweyo , funda isingeniso kwi-SQL okanye ubhalisele i-e-mail yethu ye-Learning SQL yamahhala.
Ngoku ukuba siye senza kwaye senza i-database yethu, silungele ukuqala ukudala iithebhile ezintathu ezisetyenziselwa ukugcina idatha ye-XYZ yabasebenzi. Siza kuzalisekisa iitheyibhile esilungiselelwe kwingxenye yangaphambili yale tutitshala.
Ukudala Ithebhile Yethu Yokuqala
Itafile yethu yokuqala iqukethe idatha yomuntu ngamnye kumqeshwa ngamnye wekampani yethu. Sidinga ukufaka igama lomqeshwa ngamnye, umvuzo, i-ID kunye nomphathi. Yilungelelaniso olufanelekileyo lokuhlukanisa amagama okugqibela kunye nookuqala kwiindawo ezahlukileyo ukwenza lula ukukhangela idatha nokuhlenga kwixesha elizayo. Kwakhona, siya kugcina umgcini we-task manager ngamnye ngokufaka isalathisi kwi-ID yomqeshwa we-ID kwi-rekodi yomqeshwa ngamnye. Masiqale sijonge kwitheyibhile yomsebenzi oyifunayo.
IingxeloUkuba uphawu lugcina i-ID yomphathi ngamnye kumqeshwa. Ukususela kwiirekhodi eziboniswayo, sinokucacisa ukuba uSue Scampi ngumphathi wezobini uTom Kendall noJohn Smith. Nangona kunjalo, akukho lwazi kwiziko ledatha kumphathi weSue, njengoko kuboniswe ngongeniso lwe-NULL kumqolo wakhe.
Ngoku singasebenzisa i-SQL ukudala itafile kubasebenzi bethu beenkcukacha. Ngaphambi kokuba senze njalo, makhe siqinisekise ukuba sisekhompyutheni echanekileyo ngokukhupha umyalelo we-USE:
Ngaphandle koko, "abasebenzi base-DATABASE;" Umyalelo uya kwenza umsebenzi ofanayo. Ngoku sinokukhangela umyalelo we-SQL osetyenziswayo ukudala abasebenzisi bethu itafile:
BADALA ABASEBENZI ABAKHULU (UMSEBENZI WENKQUBO AKUNYE NULL, igama elibizwa ngokuba nguVARCHAR (25) AKUKHO NULL, u-FIRST VARCHAR (25) AKUKHO NULL, ingxelo INTEGER NULL);Njengalo mzekelo ungentla, qaphela ukuba idibano yokucwangcisa ifuna ukuba sisebenzise zonke iilwimi ezinkulu ze-SQL amagama angundoqo kunye neeleta ezincinci zamakholomu anegama lomsebenzisi kunye neetafile. Umyalelo ongentla ungabonakala udidekile ekuqaleni, kodwa kunene isakhiwo esilula emva kwayo. Nantsi umbono oqhelekileyo onokucacisa izinto ngokukodwa:
DALA ITHEBULI yetafile_name (igama lenkcazelo yenkcazelo yedatha, ..., i-attribute_name ye-datatype);Iimpawu kunye neNdawo zeDatha
Kwimzekelo yangaphambili, igama letafile ngabasebenzi kwaye sifaka iimpawu ezine: umqeshwa, igama lokugqibela, igama lokuqala, kunye neengxelo. I-datatype ibonisa uhlobo lolwazi esinqwenela ukulugcina kwintsimi nganye. I-ID yomqeshwa yinkalo epheleleyo ye-integer, ngoko siya kusebenzisa i-dattiepe ye-INTEGER kwintsimi yomsebenzi kunye nensimi yokubika. Amagama omqeshwa aya kuba ngamacandelo ohlobo olude kwaye asilindele ukuba umqeshwa abe negama lokuqala okanye elide kunamahlamvu angama-25. Ngoko ke, siya kusebenzisa uhlobo lwe-VARCHAR (25) kule mimandla.
Iimpawu ze-NULL
Siyakwazi ukucacisa nokuba yi- NULL okanye NOT NULL kwinkalo yokukhetha ye-CREATE isitatimenti. Oku kuchaza nje idesitenti ukuba ngaba i-NULL (okanye ingenanto) ixabiso livumelekile kuloo mfanelo xa ufaka imigqa kwi database. Ngokomzekelo wethu, isebe le-HR lifuna ukuba i-ID yomqeshwa kunye negama elipheleleyo ligcinwe kumqeshwa ngamnye. Nangona kunjalo, akuwona wonke umsebenzi unomphathi - i-CEO ingabika mntu! - ngoko sivumela i-NULL ukungena kule ntsimi. Qaphela ukuba i-NULL yixabiso elenzekileyo kwaye ukushiya olu khetho luya kuvumela ngokupheleleyo ixabiso le-NULL malunga nombono.
Ukwakha iiTables ehleliyo
Ngoku makhe sijonge kummandla wetafile. Ukujonga ngokukhawuleza kule datha, kubonakala ngathi kufuneka sigcine i-integer kunye neenkalo ezimbini ezide. Njengomzekelo wethu wangaphambili, asilindele ukuba i-ID yesithili idle amaninzi angaphezu kwama-25. Nangona kunjalo, ezinye zeendawo zethu zinegama elide, ngoko siza kwandisa ubude obuvumelekileyo belo bhengezo kwiimpawu ezingama-40. Makhe sijonge kwi-SQL ehambelanayo:
DALA AMA-TABLE (indawo) INTEGER NOT NULL, intsimi Inkcazo I-VARCHAR (40) AKUNGAZI NULL, i-regionid VARCHAR (25) AKUKHO NULL);Ekugqibeleni, siza kusebenzisa itafile ze-EmployeeTerritories ukugcina ubudlelwane phakathi kwabasebenzi kunye nemimandla. Ulwazi olunzulu malunga nomqeshwa ngamnye nensimi lugcinwa kwiibhile ezimbini zamandulo. Ngako oko, sifuna kuphela ukugcina iinombolo ezimbini zeenombolo ezipheleleyo kule tafile. Ukuba sifuna ukwandisa le ngcaciso sinokusebenzisa i-JOIN kwimithetho yethu yokukhetha idatha ukufumana ulwazi kwiibhile ezininzi. Le ndlela yokugcina idatha iyanciphisa ukuhlengahlengiswa kwiziko lethu kwaye iqinisekisa ukusetyenziswa ngokufanelekileyo kwendawo kwindawo yokugcina. Siza kugubungela umyalelo we-JOIN ngokubanzi kwisifundo esizayo. Nantsi ikhowudi ye-SQL ukuphumeza ithebula lethu lokugqibela:
DALA AMATERITORATORS (ABASEBENZI BENKQUBO YOKUSEBENZA KUNYE), UMSEBENZI AKHONA NULL);INkqubo yeSQL inikezela ukuLungiswa koLwakhiwo lweDatabase emva kokudala
Ukuba unobulumko namhlanje, usenokuphawula ukuba "ngengozi" yashiya enye imfuno yoyilo xa sisebenzisa iithebhile zethu zeenkcukacha. Umlawuli we-HRYZ we-HR ucele ukuba ulwazi lomvuzo wemisebenzi yomgcini we-database kwaye asikuhoxiswanga ukubonelela kule tafile yedatha esiyidalile .
Nangona kunjalo, zonke azilahlekanga. Singawusebenzisa umyalelo we-ALTER TABLE ukufaka le mfanelo kwiziko lethu elikhoyo. Sifuna ukugcina umvuzo njengexabiso elipheleleyo. I-syntax ifana neyo-CREATE TABLE umyalelo, nantsi:
Qaphela ukuba sachaze ukuba ixabiso le-NULL livunyelwe kule mfanelo. Kwiimeko ezininzi, akukho nxaxheba xa ungeze ikholomu kwitafile ekhoyo. Oku kubangelwa kukuba itafile sele iqule imigqa engenakho ukungena kule mfanelo. Ngoko ke, i-DBMS ifake ngokuzenzekelayo ixabiso le-NULL ukuzalisa ukungabikho.
Kwaye kwenyusa ukujonga kwethu kwiSquL database kunye nenkqubo yokudala ithebula. Hlola ngokuphindaphindiweyo izitolimende ezintsha kwiinkomfa zethu zokufundisa ze-SQL. Ukuba ungathanda ukukhumbuza i-imeyile xa amaqaku amasha ayongezwa kwi-About database, qiniseka ukuba ubhalisele kwi-newsletter yethu!