Cov txheej txheem:
Video: Cov ntsiab lus SQL puas tuaj yeem faib hla kab?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Kev sau ntawv SQL ntawv Nqe lus
Ntsiab lus ua tsis tau faib hla kab los yog abbreviated. Clauses feem ntau yog muab tso rau ntawm nyias kab rau readability thiab yooj yim ntawm editing. Tabs thiab indents ua tau siv los ua kom cov lej nyeem tau yooj yim
Hais txog qhov no, koj siv lo lus tseem ceeb hauv SQL lus nug li cas?
Cov ntsiab lus SQL tuaj yeem siv tau raws li tau piav qhia hauv cov piv txwv hauv qab no rau ntau yam haujlwm
- Tsim. Lub CREATE Keyword yog siv los tsim cov ntaub ntawv, rooj, views, thiab ntsuas.
- TSEEM CEEB. Lo lus tseem ceeb no tshwj xeeb txheeb xyuas txhua yam ntawm cov ntaub ntawv.
- INSERT.
- Xaiv.
- Los ntawm.
- ALTER.
- Ntxiv.
- DISTINCT.
Ib yam li ntawd, lub peev xwm ntawm SQL Xaiv cov nqe lus yog dab tsi? Sau cov peev txheej ntawm SQL SELECT nqe lus
- Peb qhov kev ua haujlwm tseem ceeb uas SELECT cov lus muaj peev xwm ua tau yog qhov projection, xaiv, thiab koom nrog.
- Qhov projection yog hais txog kev txwv ntawm txhua kab uas tau xaiv los ntawm ib lub rooj.
- Kev xaiv yog hais txog kev rho tawm ntawm kab los ntawm lub rooj.
- Kev koom nrog koom nrog txuas ob lossis ntau lub rooj raws li cov yam ntxwv sib xws.
Ib yam li ntawd, koj tuaj yeem nug, dab tsi yog cov lus tshwj tseg hauv SQL?
Cov lus tseg yog SQL cov ntsiab lus thiab lwm cov cim uas muaj lub ntsiab lus tshwj xeeb thaum lawv ua tiav los ntawm Lub Cav Sib Txuas. Cov lus tseg tsis pom zoo siv los ua database, rooj, kem, hloov pauv lossis lwm yam khoom npe.
Dab tsi yog hu ua SQL?
SQL ntawv yog ib qho luv luv rau cov lus nug cov lus nug, thiab hais tias pom-kwell lossis cov ntawv cais. SQL ntawv yog cov lus nug tus qauv rau kev thov cov ntaub ntawv los ntawm cov ntaub ntawv. Tus thawj version hu ua SEQUEL (cov qauv lus nug lus Askiv) tau tsim los ntawm IBM lub chaw tshawb fawb hauv xyoo 1974 thiab 1975.
Pom zoo:
Koj puas tuaj yeem tsim ib lub rooj ntawm cov ntsiab lus hauv Bluebeam?
Kuv puas muaj Bluebeam® Revu® version twg? Revu tuaj yeem tsim cov lus ntawm cov ntsiab lus nrog txuas mus rau nplooj ntawv hauv PDF. Yog tias PDF twb suav nrog bookmarks, cov txheej txheem yooj yim li xa tawm cov bookmarks mus rau PDF tshiab, thiab tom qab ntawd ntxig cov ntawv ntawd thaum pib ntawm daim ntawv qub
Cov cai twg tuaj yeem tso cai rau cov tswv cuab ntawm lub tsev qiv ntawv cov ntsiab lus?
Cov cai uas tuaj yeem tso cai rau cov tswv cuab ntawm lub tsev qiv ntawv cov ntsiab lus (tseem hu ua chaw ua haujlwm) yam tsis tau hloov kho cov neeg siv kev tso cai yog lub peev xwm los hloov cov tswv cuab lub tsev qiv ntawv tso cai thiab koj tuaj yeem ntxiv lossis hloov cov cim npe thaum kho cov ntsiab lus
Peb puas tuaj yeem siv ob kab hauv kev faib los ntawm?
PARTITION LOS NTAWM ntau kab. PARTITION BY clause tuaj yeem siv los rhuav tshem qhov nruab nrab qhov rais los ntawm ntau cov ntaub ntawv cov ntsiab lus (kem). Piv txwv li, koj tuaj yeem suav cov hom phiaj nruab nrab ntawm lub caij nyoog thiab los ntawm lub teb chaws, lossis los ntawm lub xyoo daim ntawv qhia hnub (nrhiav los ntawm kab hnub)
Peb puas tuaj yeem siv cov lus npaj rau xaiv cov lus nug hauv Java?
Yuav siv cov lus npaj li cas rau xaiv cov lus nug hauv Java nrog MySQL? Tam sim no koj tuaj yeem tso saib tag nrho cov ntaub ntawv ntawm lub rooj siv Java PreparedStatement. Koj yuav tsum siv txoj kev executeQuery()
Dab tsi yog cov ntsiab lus ntawm cov kab lus taw qhia?
Hauv kev sau ntawv, kev taw qhia, uas tuaj yeem yog ib lossis ob kab lus, qhia lub ntsiab lus. Muaj peb ntu rau kev taw qhia: cov lus qhib, cov kab lus txhawb nqa, thiab cov ntsiab lus pib