Video: Dab tsi yog qhov kev faib tawm hauv SQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Tshaj () yog ib nqe lus uas yuav tsum tau txhais lub qhov rais nyob rau hauv cov lus nug tshwm sim. Tshaj () yog ib feem ntawm SELECT thiab ib feem ntawm cov ntsiab lus tag nrho. Lub qhov rais muaj nuj nqi suav tus nqi rau txhua kab hauv lub qhov rais. PARTITION Los ntawm expr_list. PARTITION BY yog cov lus xaiv xaiv uas muab cov ntaub ntawv rau hauv muab faib.
Tom qab ntawd, dab tsi yog sum over partition los ntawm?
SUM (Tag nrhoDue) Tshaj ( PARTITION LOS YOG CustomerID) AS 'Tag nrho Cov Neeg Muag Khoom' Qhov kev qhia no qhia SQL Server rau pawg ( muab faib ) cov ntaub ntawv los ntawm CustomerID thiab tsim cov neeg muag khoom tag nrho. Koj yuav pom tias tus nqi no zoo ib yam uas CustomerID rau kev txiav txim yog tib yam.
Tsis tas li ntawd, muab faib SQL Server yog dab tsi? Kev faib tawm yog cov txheej txheem database uas cov ntxhuav loj heev tau muab faib ua ntau qhov me me. Los ntawm kev faib lub rooj loj rau hauv cov rooj me me, cov lus nug uas nkag tau tsuas yog ib feem ntawm cov ntaub ntawv tuaj yeem khiav nrawm dua vim tias muaj cov ntaub ntawv tsawg dua los luam theej duab.
Kuj kom paub, Row_Number () yog dab tsi thiab muab faib los ntawm hauv SQL Server?
Cov Kab_Number muaj nuj nqi yog siv los muab cov lej sib law liag ntawm cov kab hauv qhov tshwm sim los ntawm qhov kev txiav txim xaiv hauv OVER clause rau txhua tus muab faib tau teev nyob rau hauv OVER clause. Nws yuav muab tus nqi 1 rau thawj kab thiab nce tus lej ntawm cov kab tom ntej.
Dab tsi yog qhov sib txawv ntawm pawg los ntawm thiab muab faib los ntawm?
13 Teb. A pab pawg los ntawm ib txwm txo tus naj npawb ntawm kab rov qab los ntawm dov lawv thiab suav qhov nruab nrab lossis cov lej rau txhua kab. muab faib los ntawm tsis cuam tshuam tus naj npawb ntawm kab rov qab, tab sis nws hloov pauv li cas lub qhov rais ua haujlwm qhov txiaj ntsig tau suav. Peb tuaj yeem ua piv txwv yooj yim.
Pom zoo:
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