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Cov ntsiab lus SQL puas tuaj yeem faib hla kab?
Cov ntsiab lus SQL puas tuaj yeem faib hla kab?

Video: Cov ntsiab lus SQL puas tuaj yeem faib hla kab?

Video: Cov ntsiab lus SQL puas tuaj yeem faib hla kab?
Video: Data Science with Python! Analyzing File Types from Avro to Stata 2024, Kaum ib hlis
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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

  1. Tsim. Lub CREATE Keyword yog siv los tsim cov ntaub ntawv, rooj, views, thiab ntsuas.
  2. TSEEM CEEB. Lo lus tseem ceeb no tshwj xeeb txheeb xyuas txhua yam ntawm cov ntaub ntawv.
  3. INSERT.
  4. Xaiv.
  5. Los ntawm.
  6. ALTER.
  7. Ntxiv.
  8. 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.

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