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MySQL ukhethe kusuka khetha: izibonelo zalokho opharetha

MySQL, njenganoma iyiphi enye zingubudlelwane ngabaphathi semininingwane uhlelo enalo oyiyo isampuli isitatimende KHETHA. Lokhu akusona isimanga, ngoba yolwazi aqukethe ulwazi oluyimfihlo ngokuyinhloko ukulithola uma kudingeka. select from SELECT позволяет делать это множеством различных способов, предоставляя большой набор инструментов. MySQL ukhethe kusukela KHETHA isitatimende ikuvumela ukuba wenze lokhu ngezindlela eziningi ezahlukene, ukuhlinzeka isethi okuhle kwamathuluzi.

Ukufaka MySQL

MySQL luyasetshenziswa njengoba ngaphansi Windows, nangaphansi Linux. Ukufaka MySQL Ubuntu, enze amaqembu amabili sasivumela at ukuphela kwe-OS:

- Sudo efaneleka-uthole ufake mysql-server.

- Sudo efaneleka-uthole ufake mysql nekhasimende lakhe.

Ukuze MySQL-Windows, nje ukulanda kusuka indawo esemthethweni "semininingwane" ezifanele ukufakwa amaphakheji futhi ugijime kubo.

Isakhiwo jikelele isitatimende KHETHA

isakhiwo Qedela e MySQL ukhethe kusukela isitatimende KHETHA simiswe ngalendlela lelandzelako:

1. KHETHA - amagama ikholomu (izinkambu).

2. FROM - etafuleni amagama.

3. LAPHO - isimo lapho lokuphuza.

Phawula ukuthi nakuba i-syntax SQL ulimi kawuzweli, umkhuba omuhle ukubhala izitatimende angukhiye agodliwe (FROM, LAPHO, njll) ngamagama amakhulu, futhi amagama amatafula namakholomu - amancane. SELECT приведен на рисунке ниже. Isibonelo kakhulu okulula usebenzisa MySQL opharetha khetha kusuka KHETHA kukhonjisiwe ngezansi.

Lwenkanyezi emva izwi KHETHA kuyinto analogue of the elisemqoka BONKE kusho ukuthi kusukela itafula unikezwa ukukhetha wonke amakholomu. Uma unesithakazelo kuphela amanye amasimu kwetafula, kufanele kuboniswe endaweni efanele, ahlukaniswe ikhefana. Kuyefana nasendleleni amagama amatafula - uma ezingaphezu kweyodwa, faka bonke ahlukaniswe ikhefana.

Ukusebenzisa LAPHO

Ngokusobala, ungase bekuqaphele ukuthi isibonelo esandulele, akukho elisemqoka LAPHO - lokhu kungenxa yokuthi kuleli cala ngayo thina akudingeki. Lesi sitatimende kungadingeki, futhi enjalo-opharetha ozikhethela e KHETHA, kunezindlela eziningi, kodwa kamuva kancane. Uma emva igama unezela itafula LAPHO futhi yimuphi umbandela, njenge-type = 'inja', bese umphumela isethi uzothola umugqa owodwa kuphela isilwane egameni Edison. Isibalo esingezansi sibonisa isibonelo. Musa Ziba isitatimende ORDER BY, lapha akunandaba, futhi kuzoxoxwa ngemva kwesikhashana.

Kuyaphawuleka ukuthi ngemva LAPHO zingenza ukubhala izimo eziningi, kodwa ayisekho ahlukaniswe ikhefana. Ngenxa yale njongo, kufanele usebenzise amagama anjengelithi KANYE noma NOMA. Konke kuncike kanjani izimo zakho okumelwe ahlangabezane nazo. Uma unesithakazelo yalokho ukuthi kwanelisa zonke izimo owacacisayo ke phakathi kwabo kumele ibe FUTHI uma umphumela okufanele ukwanelisa okungenani omunye wabo, bese usebenzisa NOMA.

ORDER BY isigatshana

We okukhulunywa ukuthi ngaphezu LAPHO esitatimendeni KHETHA kunezinye angukhiye amaningi ngawo angalawula yi setha njengoba kudingeka esimweni esithile. Esinye salezo "izihluthulelo" kuyinto ORDER BY. It ikuvumela ukuba ukuhlunga imiphumela isampula ngaphakathi lwalowo, kokubili zenyuka, zehla. Kuyinto ngokwanele ukuba nje ucacise igama ikholomu ngemuva kwakhe, ngokuvumelana amagugu ukuthi udinga ukuhlunga idatha. Kubalulekile athobele ezimeni eziningana: owokuqala - igama elicacisiwe isitatimende, ORDER BY, futhi kumelwe abe khona kuwo KHETHA; yesibili - ORDER BY kumelwe ibekwe ekupheleni isicelo.

Ukuhlela okuzenzakalelayo unyukela (ASC), kodwa uma udinga ukuhlunga imiphumela kusuka kwezinkulu kwehle, bhala emva igama emkhakheni esikhundleni ASC elisemqoka DESC.

isiphetho

Sibukeze main, kodwa hhayi wonke amathuluzi opharetha MySQL ukhethe kusuka. KHETHA, ngaphandle kwalabo okukhulunywa ngabo ngenhla, has a lot of ezinye izici evumela ukubuyisa idatha kusuka database, kalula nangokunembile.

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