Video: Dab tsi yog sparse kem Dab tsi yog qhov zoo thiab qhov tsis zoo?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Koj poob 4 bytes tsis yog ib zaug ib kab; tab sis rau txhua lub cell hauv kab uas tsis yog null. Qhov zoo ntawm SPARSE kem yog: Qhov tsis zoo ntawm SPARSE kem yog: SPARSE kem tsis tuaj yeem siv rau ntawm cov ntawv nyeem, ntext, duab, daim ntawv teev sijhawm , geometry, geography lossis cov neeg siv cov ntaub ntawv teev tseg.
Raws li, dab tsi yog sparse kem?
A SPARSE kab yog hom dog dig kem uas tau optimized cia rau NULL qhov tseem ceeb. Nws kuj txo qhov yuav tsum tau ntawm qhov chaw rau null qhov tseem ceeb ntawm tus nqi ntawm cov nyiaj siv ua haujlwm ntau dua kom rov qab tau cov nqi tsis yog null. Hauv lwm lo lus, a SPARSE kab zoo dua ntawm kev tswj NULL thiab ZERO qhov tseem ceeb hauv SQL Server.
Tsis tas li ntawd, ib qho ntawm cov cwj pwm hauv qab no yuav tsum tau siv los ua kom zoo rau kev khaws cia rau qhov tsis muaj nuj nqis? Sparse kab muaj cov raws li yam ntxwv: SQL Server Database Cav siv SPARSE lo lus tseem ceeb hauv kab lus txhais rau ua kom zoo tus khaws cia ntawm tus nqi hauv kem ntawd. Yog li ntawd, thaum kab tus nqi yog NULL rau txhua kab hauv lub rooj, lub tus nqi xav tsis muaj khaws cia.
Hais txog qhov no, dab tsi yog sparse kab hauv SQL Server 2008?
SQL Server 2008 qhia txog lub tswvyim sparse kem , uas yog ib hom kem uas optimizes cia rau cov nqi null. Thaum a kem muaj ib tug xov tooj ntawm null qhov tseem ceeb, txhais cov kem raws li nyias tuaj yeem txuag tau ntau qhov chaw disk.
Cov ntaub ntawv sparse yog dab tsi?
Txhais: Cov ntaub ntawv loj Ib variable nrog cov ntaub ntawv sparse yog ib qho uas feem pua ntawm cov hloov pauv ntawm cov hlwb tsis muaj qhov tseeb cov ntaub ntawv . Xws li "npliag," lossis NA, qhov tseem ceeb siv qhov chaw cia hauv cov ntaub ntawv.
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