Mukufuna uphungu pogwiritsa ntchito Language Structured Query ? Malemba awa SQL FAQ akupereka mayankho kwa mafunso omwe amafunsidwa kawirikawiri pa SQL ndi mabungwe. Onetsetsani kuti mukutsatira zowonjezera "Zambiri" kumapeto kwa funso lirilonse kuti mudziwe zambiri ndi zomwe mukuphunzira.
01 pa 10
Kodi ndingapeze bwanji deta kuchokera ku database pogwiritsa ntchito SQL?
Lamulo la SELECT ndilo lamulo lofala kwambiri pa SQL. Amalola anthu ogwiritsa ntchito malo osungirako malonda kuti adziwe zomwe iwo akufuna kuchokera kuntchito yogwirira ntchito. Zambiri "
02 pa 10
Kodi ndimapanga bwanji deta yatsopano kapena tebulo latsopano?
SQL imapereka CREATE DATABASE ndi CREATE MALAMULO malamulo kuti muwonjezere zida zatsopano ndi matebulo, motsatira ndondomeko yanu. Malamulo awa amapereka syntax yosinthasintha kwambiri kukulolani kupanga matebulo ndi mazenera omwe amakwaniritsa malonda anu enieni. Zambiri "
03 pa 10
Kodi ndikuwonjezera bwanji deta ku database?
Lamulo la INSERT mu SQL limagwiritsidwa ntchito kuwonjezera zolemba ku tebulo lomwe liripo.
04 pa 10
Ndingathetse bwanji kapena tebulo lonse lamasamba?
Kawirikawiri, zimakhala zofunikira kuchotsa zosavuta kuzimvetsa kuchokera ku deta yolumikizana. Mwamwayi, Language Structured Query imapereka lamulo losasintha la DELETE lomwe lingagwiritsidwe ntchito kuchotsa zina kapena zonse zomwe zasungidwa mu tebulo. Zambiri "
05 ya 10
Kodi mtengo wa NULL ndi chiyani?
NULL ndi mtengo wogwiritsidwa ntchito kuimira gawo losadziwika la deta. Zomwe zimagwiritsira ntchito mfundo za NULL mwanjira yapadera, malingana ndi mtundu umene amagwiritsiridwa ntchito. Pamene mtengo wa NULL umawonekera ngati opita ku NTCHITO, mtengo wa opaleshoni uli WOSACHITA ngati ntchito ina ndi yosavuta (palibe njira mawuwo akhoza kukhala OONA ndi opanga imodzi FALSE). Kumbali ina, zotsatira zake ndi NULL (osadziwika) ngati china ntchito ndi TRUE kapena NULL (chifukwa sitingathe kudziwa chomwe chidzakhale chomwecho). ยป
06 cha 10
Kodi ndingatani kuti ndiphatikize deta kuchokera ku matebulo ambirimbiri?
SQL yowonjezera mawu amakulolani kuti muphatikize deta kuchokera pa matebulo awiri kapena angapo muzotsatira zanu. Phunzirani momwe mungagwiritsire ntchito luso lamakono lamtunduwu kuti mupitirize kufufuza mafunso anu.
07 pa 10
Kodi ndingalowe nawo tebulo?
Inde! Mungagwiritse ntchito kudziphatika nokha kuti mukhale ndi mafunso ochepa a SQL omwe muli malo omwe mkati ndi kunja akunena tebulo lomwelo. Amenewa amaloledwa kukulolani kuti mutenge zolemba zokhudzana ndi tebulo lomwelo.
08 pa 10
Ndingathe bwanji kufotokozera mwachidule deta yomwe ili mu tebulo lachinsinsi?
SQL imapereka ntchito zambiri kuti zithandizire ndi kufotokoza mwachidule mavoti ambiri a deta. Ntchito ya SUM imagwiritsidwa ntchito mkati mwa ndondomeko ya SELECT ndipo imabweretsanso chiwerengero cha zikhulupiliro. Ntchito ya AVG imagwira ntchito mofananamo kuti ikhale ndi chiwerengero cha masamu pazinthu zoyenera. SQL imapereka ntchito COUNT kuti ipeze nambala ya ma tebulo omwe akutsatiridwa ndi zoyenera. Ntchito ya MAX () imabweretsanso mtengo waukulu kwambiri pazinthu zadongosolo pamene MIN () ntchito ikubwezera mtengo wochepa kwambiri.
09 ya 10
Kodi ndingapeze bwanji deta mwachidule?
Mungagwiritse ntchito mafunso oyambirira a SQL kuti mupeze data kuchokera ku databata koma izi nthawi zambiri sichipatsa nzeru zokwanira kuti zikwaniritse zofunikira za bizinesi. SQL imakupatsaninso kuti mutha kuyambitsa zotsatira zazokambirana zogwirizana ndi zikhalidwe za mzere wa mzere kuti mugwiritse ntchito ntchito zambiri pogwiritsa ntchito clause GROUP BY. Zambiri "
10 pa 10
Kodi ndingapewe bwanji mwayi wopezeka ku deta yomwe ili mu database ya SQL?
Masamba a SQL amapereka olamulira omwe ali ndi gawo loyang'anira njira zowunikira. Mu schema iyi, otsogolera amapanga osuta makasitomala a munthu aliyense wogwiritsa ntchito deta ndikusankhira munthu wogwiritsa ntchito deta imodzi kapena zingapo zomwe zimagwiritsa ntchito momwe wogwiritsira ntchito amaloledwa kuyanjana ndi database. Potsirizira pake, woyang'anira amapereka zilolezo zenizeni pa udindo kuti alole kuti mamembala achite zofunazo. Ogwiritsidwanso akutsutsa mwatsatanetsatane mwayi uliwonse umene sakupatsidwa mwachindunji. Zambiri "