SQL "for Dummies": into ekufuneka uyazi lo mfundi?

Ukuza kuthi ga ngoku, "kuba Dummies" iikhosi SQL yaye kuya kusanda ukuthandwa. Kunokuba lula kakhulu ukucacisa, ngenxa yokuba kaninzi ungenza ekuthiwa iinkonzo web 'amakhulu' ehlabathini ukufumana namhlanje. Ukuba izizathu esingxotyeni bhetyebhetye kwaye zisekelwe phezu zolwazi. Bonke badwelisi benkqubo makhwelo abaye bagqiba kwelokuba azinikele ekudalweni kweendawo, yabhalelwa kwiikhosi SQL "for Dummies".

Kutheni bafunde ulwimi?

Kuqala kwinto zonke, SQL lufundiswe ukuze ukuqhubela ukudaleka iintlobo ngeentlobo izicelo omnye ethandwa kakhulu ukuze iinjini umhla blog - WordPress. Emva ekupaseni izifundo ezimbalwa ezilula, uya sele bakwazi ukuyila imibuzo nayiphi ukuntsokotha, nto leyo eqinisekisa kuphela lula ulwimi.

Yintoni SQL?

Ingxaki yokwakhiwa kolwimi, okanye Ingxaki yokwakhiwa kolwimi, wadalwa nenjongo eyodwa: ukugqiba udidi lwe data, ukubonelela ukufikelela kubo sibaphathe ngendlela kumathuba nje elingephi. Ukuba uyazi SQL-value, Uya kwandula ukukuqonda ukuba lo mncedisi fanele ku ebizwa ngokuba iilwimi "nonprocedural". Okt ukukwazi kwalo ukuba kubandakanye kuphela inkcazo yalo naluphi na yeekhomponenti okanye iziphumo ukuba ufuna ukubona kwixesha elizayo kule sayithi. Kodwa lo wenkqubo ayicacisi ukuba yintoni kanye eza ukufumana iziphumo. isicelo ngasinye esitsha kolu ulwimi luhlobo extra "superstructure." Ngaloo Ukuze apho wangena kwi-database, yaye iza kuzaliseka izicelo.

Zeziphi iinkqubo zingenziwa ngokusebenzisa olu lwimi?

Nangona elula, zesiseko sedata ze SQL ikuvumela ukuba ukudala ezininzi izicelo kakhulu abohlukeneyo. Ngoko yintoni onokuyenza xa ufunda eli ulwimi ebalulekileyo lokuprograma?

• ukwakha iintlobo ngeentlobo iitafile;
• kwamkela, ivenkile, uze uguqule idatha;
• ukutshintsha isakhiwo yezintlu ngokubona kwayo;
• ahlanganise ulwazi zifunyenweyo iyunithi eyodwa;
• ukubala idatha eyafunyanwa;
• ukunika ukhuseleko ngokupheleleyo nolwazi.

Zeziphi amaqela kakhulu liyathandwa kweli lwimi?

Ukuba ugqiba ukutyelela khosi SQL "for Dummies", ngoko ke uya kufumana inkcazelo eneenkcukacha malunga imiyalelo ezisetyenziswa ekudaleni imibuzo nayo. Avamise kakhulu ukuza kuthi ga ngoku zezi zilandelayo:

1. DDL - yinto umyalelo ikhankanya i data. Isetyenziswa ukudala, ulungise uze ususe iindidi zezinto kwiziko ledatha.
2. DCL - iqela elawula data. Oku kusetyenziswa ukubonelela ufikelelo kubasebenzisi ezahlukeneyo ulwazi kwi-database, ngokunjalo ukusebenzisa itafile okanye umbono.
3. TCL - yeqela ilawula iintlobo ezahlukeneyo zoshishino. Injongo yalo esentloko kukuba ukumisela indlela yalo yingisela.
4. DML - iqhatha idata ifunyenwe. Injongo yalo kuvumela umsebenzisi ukuba ukususa iintlobo ulwazi kuvimba okanye negalelo kuyo.

Iindidi amalungelo ezikhoyo kule server

Phantsi ilungelo libhekisa kwabo iintshukumo uyakwazi ukwenza enye okanye omnye umsebenzisi ngokwendlela isimo sabo. Osezantsi, Kakade ke, ngemvume eqhelekileyo. Kakade ke, ekuhambeni kwexesha amalungelo yaye zisenokutshintshwa. Old zingacinywa ezintsha longeziwe. Ukususela namhlanje, bonke abo abadlula izifundo Kumncedisi we SQL "for Dummies", uyazi ukuba kukho iintlobo zemisebenzi okuvumelekileyo:

1. uhlobo lwento - umsebenzisi uvumelekile ukuba enze nawuphi na umyalelo kuphela ngokunxulumene into ethile into ledatha. Ngelo xesha lokuba izinto ezahlukeneyo amalungelo ezahlukeneyo. Kananjalo apha nje kuphela umsebenzisi othile, kodwa iitafile. Ukuba umntu usebenzisa izakhono zabo, mna ndadala itafile, ngoko kucingwa ukuba ube ngumnikazi wayo. Ngoko ke, xa ilungelo lakhe ukuba amisele amalungelo entsha abanye abasebenzisi ezinxulumene ne ulwazi kuyo.
2. uhlobo System - ulwazi ekuthiwa-copyright. Abathengi bafumana loo malungelo, ungenza iindidi zezinto kwiziko ledatha.

Imbali kwi SQL

Olu lwimi wenziwa ngu IBM ngo-1970, lo yolaborathri yophando. Ngoxa igama lakhe eyahlukileyo kancinane (enye), kodwa emva kweminyaka embalwa ukusetyenziswa, itshintshe, kunciphisa bit. Ngaphandle koku, nanamhlanje, iingcali yamazwe ngamazwe iinkqubo ezininzi ezaziwayo-kakuhle nangoku ukulibiza igama endala. SQL wadalwa kunye nenjongo enye - ukuba zizakhele ulwimi eyayiza kuba lula ukuba likwazi ngaphandle naziphi na iingxaki ukufunda abasebenzisi Internet elula. An into umdla kukuba ngoxa SQL wayengekho ulwimi kuphela. E California, elinye iqela leengcaphephe liqulunqe Ingres efanayo, kodwa yena akazange abe ngokubanzi. De 1980, kwakukho oomahluko eziliqela ze SQL, ezo kuphela kumlinganiselo othile kwahluka enye kwenye. Ukuthintela ukudideka, ngo-1983, lo uhlobo umgangatho sele yenziwe, nto leyo ithandwayo namhlanje. Iikhosi SQL "for Dummies" akuvumela wazi okungakumbi ngale nkonzo kunye ngokupheleleyo aligocagoce iiveki ezimbalwa.