Indlela ukubhala SQL-imibuzo - izibonelo ezinemininingwane

Ngamunye wethu ubhekene njalo abuye asebentise ezihlukahlukene yolwazi. Lapho sikhetha ikheli le-imeyili, sisebenzela nge database. egciniwe usebenzisa amasevisi wokusesha, amabhange isitoreji idatha ikhasimende, njll

Kodwa naphezu ukusetshenziswa njalo database, ngisho izinhlelo eziningi isofthiwe Onjiniyela eziningi "amabala amhlophe" ngenxa ukutolika ahlukene imigomo efanayo. Sinikeza incazelo emfushane imigomo esemqoka ukuze yolwazi SQL ukucabangela. Kanjalo.

Database - ifayela noma usethe amafayela ukugcina ngaphambilini idatha izakhiwo nobudlelwano bawo. Isikhathi esining impela, database ibizwa ngokuthi uhlelo lokuphathwa egciniwe (DBMS). Database - kungcono nje onalo kolwazi ngefomethi ethize futhi bangasebenza yolwazi ehlukene.

Ithebula - ukucabanga ifolda lapho imibhalo egcinwe, babeqoqana ngokuvumelana nemingcele ethile, njengengcebo uhlu oda ngenyanga edlule. Lena isithebe computer database. A ithebula ahlukene unegama yaso ehlukile.

Idatha Uhlobo - nohlobo lokwaziswa bavunyelwe kwi-ikholomu eyodwa noma umugqa. Kungaba ethize inombolo noma umbhalo format.

Ikholomu nomugqa - sonke sasebenza nge-spreadsheet, nayo ekhona imigqa namakholomu. Noma yimuphi semininingwane zingubudlelwane isebenza nge amatafula ngendlela efanayo. Strings babizwe ngokuthi amarekhodi.

Isihluthulelo esiyinhloko - emgqeni ngamunye angase abe munye noma ngaphezulu izinsika ukuhlonza layo eliyingqayizivele. Ayikho ukhiye oyihloko kunzima kakhulu ukuba ubuyekeze, lungisa futhi susa imigqa efanele.

Kuyini SQL?

Umbuzo ulimi SQL (IsiZulu Ulimi Lokusebenza Oluhlelekile -. Ulimi Lokusebenza Oluhlelekile) lwenzelwe kuphela ukusebenza yolwazi futhi okwamanje indinganiso zonke yolwazi ethandwa. I-syntax ulimi yakhiwa inombolo encane opharetha futhi kulula ukufunda. Kodwa nakuba isikhona lula sobala, kuvumela ukudalwa imibuzo SQL imisebenzi eziyinkimbinkimbi database yabo bonke ubukhulu.

Kusukela ngo-1992, kukhona elifanayo, ngokuthi ANSI SQL. Kuchaza syntax eziyisisekelo nemisebenzi opharetha futhi isekelwa bonke abaholi DBMS emakethe, ezifana Oracle Microsoft Server SQL. Cabanga zonke izici ulimi isihloko iDemo akunakwenzeka, ngakho sizohlola kafushane kuphela eziyisisekelo imibuzo SQL. Izibonelo khombisa ubulula izici ulimi:

• ukudala yolwazi namathebula;
• Ukukhetha idatha;
• Ukungeza okufakiwe;
• ukuguqulwa kanye nokususwa kolwazi.

SQL Idatha Izinhlobo

Zonke amakholomu itafula semininingwane ukugcina efanayo uhlobo idatha. e SQL nedatha ziyefana ngezinye izilimi izinhlelo.

uhlobo lwedatha	incazelo
INT	integers
YANGEMPELA	Floating iphuzu izinombolo
UMBHALO	Uhlamvu string ubude variable
DATE	Umbuzo SQL "usuku" ezihlukahlukene ifomethi
ISIKHATHI	isikhathi
CHAR	Umbhalo izintambo obuphelele okungaguquki

Yakha amathebula zemininingwane

Dala yolwazi olusha, amatafula, nezinye imibuzo SQL Kunezindlela ezimbili yilezi:

• izitatimende SQL ngokusebenzisa console semininingwane
• Usebenzisa amathuluzi interactive Administration, ingxenye leseva database.

A imininingo egciniwe emisha opharetha DALA EGCINIWE ; . Njengoba ubona, syntax ilula sikubeke.

Lamathebuli ngaphakathi semininingwane ukudala DALA ITHEBULA isitatimende nemingcele ezilandelayo:

• igama lethebula
• amagama kanye nedatha izinhlobo amakholomu

Njengoba isibonelo, udale ithebula Lezimpahla ne amakholomu ezilandelayo:

ikholomu	incazelo
commodity_id	ID yomkhiqizo
VENDOR_ID	ID Umthengisi (Abathengisi Key ithebula langaphandle)
commodity_name	igama lomkhiqizo
commodity_price	izindleko
commodity_desc	incazelo

Dala uhlu:

DALA ITHEBULA Lezimpahla

(CHAR commodity_id (15) HHAYI null,

VENDOR_ID CHAR (15) HHAYI null,

commodity_name CHAR (254) null,

commodity_price idesimali (8.2) null,

commodity_desc VARCHAR (1000) null);

Ithebula linamakholomu ezinhlanu. Ngemva igama uhlobo idatha zinsika zinhle ahlukaniswe ikhefana. Inani kukholomu kuthathwa amagugu null (null) noma kufanele igcwaliswe (HHAYI null), futhi uzimisele ukuze udale ithebula.

Idatha eyisampula kusukela ithebula

idatha amasampuli opharetha - lo ajwayele ukusetshenziswa kakhulu imibuzo SQL. Ukuze uthole olunye ulwazi udinga ukucacisa ukuthi sifuna ukukhetha kusuka etafuleni. Ekuqaleni isibonelo esilula:

commodity_name KHETHA KUSUKELA Lezimpahla

Ngemva isitatimende KHETHA ukhombise amagama kwekholomu ukuthola ulwazi, kodwa KUSUKELA ikhomba etafuleni.

umphumela nombuzo kuyoba yonke imigqa etafuleni nge Commodity_name ngemagugu ngokulandelana kwazo base sangena database isb ngaphandle ekuhlungeni. Ukuze uhlele imiphumela usebenzisa ozikhethela opharetha ORDER BY.

Ukuze ukhononda emasimini amaningi zibhale kuhlukaniswe ukhefane njengoba kulesibonelo ezilandelayo:

commodity_id KHETHA, commodity_name, commodity_price KUSUKELA Lezimpahla

Kungenzeka ukuba athole umphumela Inani lombuzo intambo ye wonke amakholomu. Ngenxa yale njongo, uphawu "*":

* KHETHA KUSUKELA Lezimpahla

• KHETHA ngaphezu kwalokho isekela:
• idatha Uhlobo (ORDER BY isitatimende)
• Ukukhethwa ngokuvumelana nemibandela (LAPHO)
• Ukubuthelela eside (GROUP BY)

engeza umugqa

Ukwengeza imigqa itafula usebenzisa izitatimende SQL nesitatimende FAKA. Ukwengeza zingenziwa ngezindlela ezintathu:

• engeza umugqa omusha lonke;
• komugqa;
• nombuzo imiphumela.

Ukwengeza umugqa ephelele, kumele ucacise igama ithebula kanye namagugu lamakholomu (izinkambu) umugqa omusha. Nasi isibonelo:

Ufake Lezimpahla IZIMO ( '106', '50', 'Coca-Cola, ' 1,68 ',' Ayikho Alcogol,)

Isibonelo unezela umkhiqizo omusha ukuba etafuleni. Amanani esibekiwe emva IZIMO ngoba ikholomu ngayinye. Uma kungekho i-value esihambisanayo ikholomu, kubalulekile ukuba ucacise null. Lezi zinsika zinhle egcwele yamanani oda ecacisiwe uma udala itafula.

Endabeni ngokungeza kuphela ingxenye string kumele ngokucacile ucacise igama kukholamu, njengasezulwini Isibonelo:

FAKA EKUDLENI Lezimpahla (commodity_id, VENDOR_ID, commodity_name)

IZIMO ( '106', '50', 'Coca-Cola, )

Sesisungule uhlelo lomnotho olubizwa izikhombi umkhiqizo kuphela, komphakeli igama layo, futhi lonke emkhakheni sibeke eceleni awunalutho.

Ukungeza nombuzo imiphumela

Ngokuyinhloko, FAKA isetshenziswa ukwengeza irowu, kodwa kungasetshenziswa for ngokungeza KHETHA isitatimende imiphumela.

ushintsho idatha

Ukushintsha imininingwane emasimini ithebula semininingwane kudingeke usebenzise isitatimende UPDATE. I-opharetha ingasetshenziswa ngezindlela ezimbili:

• Kubuyekeziwe yonke imigqa kuthebula.
• Kuphela umugqa ezithile.

UPDATE inezigaba ezintathu eziyinhloko:

• itafula lapho ufuna ukwenza izinguquko;
• amagama ensimini kanye namagugu abo amasha;
• Imibandela ukuze izinguquko Ukukhetha ilandelana.

Cabangela nasi isibonelo. Ake sithi lo mkhiqizo nge-ID = 106 ushintshe intengo, ngakho lo mugqa ukuvuselela. Bhala isitatimende esilandelayo:

UPDATE Lezimpahla ISETHI commodity_price = '3.2' LAPHO commodity_id = ' 106'

Thina waveza igama lethebula, e Kulokhu, Lezimpahla okuzokwenziwa ukuvuselelwa, bese emva SET - ukubaluleka entsha kukholamu futhi uthole into efiselekayo, ecacisa Inani lobunikazi LAPHO oyifunayo.

Ukushintsha inombolo yamakholomu emva isitatimende ISETHI icacisa amabhangqa amaningana ikholomu-value, ahlukaniswe ikhefana. Bona isibonelo lapho igama intengo izimpahla olusha:

UPDATE Lezimpahla ISETHI commodity_name = 'Fanta' , commodity_price = '3.2' LAPHO commodity_id = ' 106'

Ukususa ulwazi kukholamu, ungasetha yona null, uma uvumela isakhiwo etafuleni. Kumele kukhunjulwe ukuthi null - lena "cha" inani, hhayi zero njengoba umbhalo noma izinombolo. Susa incazelo lento:

UPDATE Lezimpahla ISETHI commodity_desc = null LAPHO commodity_id = ' 106'

Ukususa imigqa

izicelo SQL ukususa imigqa kuthebula kuyenziwa opharetha SUSA. Kunezindlela ezimbili ukusebenzisa yilezi:

• Ithebula lisusiwe imigqa ethile;
• wasusa zonke imigqa kuthebula.

ISIBONELO ukususa esisodwa umugqa ithebula:

SUSA KUSUKELA Lezimpahla LAPHO commodity_id = '106'

Ngemva SUSA KUSUKELA Icacisa igama ithebula lapho ukususa imigqa. LAPHO u-opharetha kufaka hlangana ubujamo umugqa izokhetheka ngaphansi kwazo ukuze kucis. Kusibonelo sisusa umkhiqizo line nge ID = 106. LAPHO abonisa kubaluleke kakhulu ngoba uyidlule le privedt opharetha ukususa yonke imigqa kuthebula. Lokhu kusebenza ukushintsha amanani ensimini.

Isitatimende SUSA alisho amagama ikholomu, futhi meta-izinhlamvu. Yena ngokuphelele kususa umugqa bese ususa ikholomu eyodwa, akakwazi.

Ukusebenzisa SQL e Finyelela Microsoft

Microsoft Ukufinyelela ngokuvamile esetshenziswa interactively ukudala isipredishithi, egciniwe, izinguquko ukuphatha, ukuhlaziya idatha database ukuze lelisu Finyelela imibuzo SQL nge elula interactive umbuzo Umakhi (Umbuzo Umklami), usebenzisa ongasisebenzisa ekwenzeni nokwenza izitatimende SQL ngokushesha iyiphi yinkimbinkimbi.

Futhi asekelwe Imodi ukufinyelela iseva, lapho Finyelela egciniwe ingasetshenziswa njengendlela SQL-nombuzo generator kunoma ODBC yomthombo wedatha. Lesi sici kwenza izicelo ukuxhumana Finyelela egciniwe kunoma yisiphi isakhiwo.

SQL izandiso

Ngenxa imibuzo SQL akudingeki zonke zenqubo izici ulimi lokwakha izinhlelo ezifana izihibe, ekhelini, njll, abakhiqizi DBMS ukuthuthukisa enguqulweni yawo SQL nge izici ezithuthukile. Eyokuqala usekelo izinqubo egcinwe futhi opharetha ejwayelekile izilimi zenqubo.

Imixhantela ezivame kakhulu ulimi:

• Oracle Database - PL / SQL
• Interbase, Firebird - PSQL
• Microsoft SQL Server - transact-SQL
• PostgreSQL - PL / pgSQL.

SQL Inthanethi

MySQL semininingwane ikhishwe ngaphansi kwelayisensi khulula GNU General Public License. Kukhona ilayisensi yokuhweba nge ikhono ukuthuthukisa ngokwezifiso amamojuli. Njengengxenye ingxenye ethandwa iningi amaseva Yakha Inthanethi ezifana XAMPP, WAMP futhi LIYISIBANI, futhi ithandwa kakhulu ukuthuthukiswa semininingwane isicelo ku-inthanethi.

Lwakhiwe nge-Sun Microsystems futhi okwamanje Oracle. Isekela semininingwane usayizi kuze kufinyelele 64 terabytes, syntax SQL: 2003, ukuzandisa yolwazi kanye nezinsizakalo efwini.