Video: Dab tsi yog kev siv cov clause hauv SQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
SQL ntawv | SIV Clause . Yog tias ob peb kab muaj tib lub npe tab sis cov ntaub ntawv tsis sib xws, NATURAL JOIN lus tuaj yeem hloov kho nrog cov SIV clause los qhia cov kab uas yuav tsum tau siv rau EQUIJOIN. SIV Clause yog siv kom phim ib kem nkaus xwb thaum ntau tshaj ib kab ntawv sib tw.
Yog li ntawd, dab tsi yog txoj haujlwm ntawm kev siv clause?
SIV clause . Cov SIV clause qhia cov kab ntawv twg los ntsuas qhov sib npaug thaum ob lub rooj sib koom. Nws tuaj yeem siv los hloov ON lus hauv JOIN cov haujlwm uas muaj kev koom nrog lus.
Qhov thib ob, cov nqe lus twg yuav tsum muaj nyob rau hauv cov lus nug SQL? Xaiv
Ib tug kuj yuav nug, dab tsi yog kev siv ntawm lo lus tseem ceeb hauv SQL?
Hauv qhov nutshell, koj siv ON rau ntau yam, tab sis SIV yog ib qho yooj yim shorthand rau qhov xwm txheej uas cov npe kab yog tib yam. Piv txwv saum toj no siv qhov ON lo lus tseem ceeb , tab sis txij li cov kab peb siv mus koom yog hu ua owners_id nyob rau hauv ob lub rooj, ces peb tuaj yeem muab tso rau hauv USING raws li ib tug shorthand.
Dab tsi yog siv thiab clause?
Kev koom ua ke rau kev koom nrog ntuj yog ib qho kev sib koom ua ke ntawm cov npe zoo tib yam. ON lus tuaj yeem siv los koom nrog cov kab uas muaj npe sib txawv. Siv ON lus txhawm rau txheeb xyuas cov xwm txheej lossis qhia cov kab kom koom nrog. Txoj kev koom nrog yog cais los ntawm lwm yam kev tshawb nrhiav.
Pom zoo:
Dab tsi ntawm cov hauv qab no yog qhov zoo ntawm kev siv cov khoom siv pom kev hauv kev hais lus?
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