Video: Yuav ua li cas logical tswv siv nyob rau hauv tsim database queries?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Boolean cov neeg ua haujlwm . Boolean cov neeg ua haujlwm yog siv lim databases siv THIAB, LOSSIS lossis TSIS TAU. Lawv tuaj yeem tshawb nrhiav ntau qhov chaw tib lub sijhawm los pab peb khaws cov ntaub ntawv uas peb xav tau. Lawv yog siv vim lawv muab cov txiaj ntsig uas yog 'tseeb' lossis 'false'.
Yog li ntawd, dab tsi yog cov tswv yim logical hauv database?
Logical Operators . Cov Logical operators yog cov uas muaj tseeb los tsis tseeb. Lawv rov qab qhov tseeb lossis qhov tsis tseeb los muab ib lossis ntau qhov tseeb lossis qhov tsis tseeb. Logical THIAB sib piv ntawm ob Booleans raws li kev qhia thiab rov qab muaj tseeb thaum ob qho kev qhia muaj tseeb
Ib yam li ntawd, qhov sib txawv ntawm kev siv thiab/los yog cov neeg ua haujlwm hauv cov lus nug yog dab tsi? Cov Qhov txawv ntawm THIAB & LOS YOG Cov Lus Qhia hauv Form Logic. OrgSync's form logic tso cai rau koj los teeb tsa cov kev cai uas yuav tsum tau ua kom pom cov nplooj ntawv. Thaum sib txuas ob daim logic, 'AND' qhia tias ob qho xwm txheej yuav tsum tau ua rau nplooj ntawv qhia thaum 'OR' qhia tias tsuas yog ib qho xwm txheej yuav tsum tau ua.
Khaws qhov no hauv kev txiav txim siab, dab tsi yog cov tswv yim tsim nyog hauv SQL?
Muaj peb Logical Operators yog, THIAB, LOSSIS, thiab TSIS. Cov no cov neeg ua haujlwm sib piv ob yam xwm txheej ntawm ib lub sij hawm los txiav txim seb ib kab twg tuaj yeem raug xaiv rau qhov tso zis. Thaum khaws cov ntaub ntawv siv SELECT nqe lus, koj tuaj yeem siv logical operators nyob rau hauv WHERE clause, uas tso cai rau koj los ua ke ntau tshaj ib qho xwm txheej.
Tus neeg teb xov tooj logical rov qab los rau qhov tseeb li cas?
Logical LOSSIS tus neeg ua haujlwm : Tus '||' tus neeg teb xov tooj rov qab muaj tseeb txawm tias ib (los yog ob) ntawm cov tej yam kev mob nyob rau hauv kev txiav txim siab yog txaus siab. Txwv tsis pub nws rov qab los cuav. Piv txwv li, ib || b rov qab muaj tseeb yog ib tug los yog b los yog ob leeg muaj tseeb (i.e. tsis yog xoom). Tau kawg, nws rov qab muaj tseeb thaum ib thiab b yog muaj tseeb.
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