Cov txheej txheem:
- Txawm hais tias muaj ntau hom xauv, plaub feem ntau yog padlocks, deadbolts, knoblocks, thiab levers
Video: Vim li cas xauv qhov tseem ceeb hauv SQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
SQL ntawv Server xauv yog cov qhov tseem ceeb ib feem ntawm qhov yuav tsum tau cais tawm thiab nws ua haujlwm rau xauv cov khoom cuam tshuam los ntawm kev lag luam. Thaum cov khoom muaj kaw , SQL ntawv Server yuav tiv thaiv lwm yam kev hloov pauv los ntawm kev hloov pauv ntawm cov ntaub ntawv khaws cia hauv cov khoom cuam tshuam los ntawm kev yuam xauv.
Hauv qhov no, SQL xauv yog dab tsi?
Xauv : Xauv yog ib tug mechanism los xyuas kom meej cov ntaub ntawv sib xws. SQL ntawv Server xauv khoom thaum qhov kev sib pauv pib. Thaum qhov kev hloov pauv tiav lawm, SQL ntawv Server tso tawm cov kaw khoom. Tshwj xeeb (X) Locks : Thaum no xauv hom tshwm sim, nws tshwm sim los tiv thaiv lwm yam kev hloov pauv lossis nkag mus rau a kaw khoom.
Kuj Paub, hom kev xauv hauv SQL Server yog dab tsi? SQL neeg rau zaub mov muaj ntau dua 20 ntau hom kev ntsuas phoo tab sis tam sim no cia peb tsom mus rau qhov tseem ceeb tshaj plaws.
- Shared locks (S). Cov xauv no tau txais los ntawm cov neeg nyeem thaum nyeem cov haujlwm xws li SELECT.
- Exclusive xauv (X).
- Hloov tshiab xauv (U).
- Lub hom phiaj xauv (IS, IX, IU, thiab lwm yam).
Tsis tas li ntawd, vim li cas peb thiaj li xauv lub database?
A database xauv yog siv rau “ xauv Qee cov ntaub ntawv hauv a database yog li ntawd ib leeg xwb database tus neeg siv / ntu tuaj yeem hloov kho cov ntaub ntawv tshwj xeeb. Yog li ntawd, database locks muaj rau tiv thaiv ob lossis ntau dua database cov neeg siv los ntawm kev hloov kho tib lub caij nyoog ntawm cov ntaub ntawv tib lub sijhawm.
Dab tsi yog qhov txawv ntawm cov xauv?
Txawm hais tias muaj ntau hom xauv, plaub feem ntau yog padlocks, deadbolts, knoblocks, thiab levers
- Padlocks.
- Deadbolts.
- Knob Locks.
- Lever Handle Locks.
- Cam xauv.
- Rim / Mortise Locks.
- Euro Profile Lub tog raj kheej.
- Phab ntsa Mounted Locks.
Pom zoo:
Dab tsi yog qhov xauv thiab qhov tseem ceeb ntawm kev sib raug zoo?
Cia peb muab tus yuam sij thiab xauv Lub xauv hauv qhov ntsiab lus no yog hais txog lub siab ntawm tus neeg uas poob rau hauv kev hlub thiab tus yuam sij yog hais txog tus neeg uas muaj tus neeg ntawd tus yam ntxwv ntawm kev hlub
Lo lus xauv thiab qhov tseem ceeb txhais li cas?
Hauv qab xauv thiab qhov tseem ceeb. kab lus [PHRASE tom qab verb] Yog hais tias ib yam dab tsi los yog ib tug neeg raug kaw nyob rau hauv lub xauv thiab qhov tseem ceeb, lawv nyob rau hauv ib lub thawv los yog chav tsev uas tau raug kaw ruaj ntseg. Cov phau ntawv tau ib txwm khaws cia hauv qhov xauv thiab qhov tseem ceeb hauv lub tsev qiv ntawv vault
Peb puas tuaj yeem ntxig ntau qhov NULL qhov tseem ceeb hauv qhov tseem ceeb Oracle?
Ntawd yog: Thaum (1, 1, null) raug tso cai, tab sis tsis pub ntau tshaj ib zaug, kab uas muaj qhov tseem ceeb (null, null, null) hauv peb kab uas ua rau tus yuam sij tshwj xeeb raug tso cai txhua lub sijhawm - ib yam li nyob rau hauv ib kab ke
Vim li cas qhov kev ntsuam xyuas qhov tsis zoo yog qhov tseem ceeb?
Cov txheej txheem ntsuam xyuas qhov tsis zoo yuav pab txo qis txoj hauv kev uas tus neeg tawm tsam tuaj yeem ua txhaum lub koom haum IT systems - ua kom nkag siab zoo dua ntawm cov cuab tam, lawv qhov tsis zoo, thiab tag nrho cov kev pheej hmoo rau lub koom haum
Vim li cas yog vim li cas ib txoj hauv kev tseem ceeb ntawm kev paub?
Yog vim li cas thiaj paub. Yog vim li cas feem ntau suav hais tias tsis muaj nuj nqis los ntsuas seb qhov kev lees paub, lossis txawm tias tib neeg, puas ntseeg tau. Yog vim li cas qee zaum sib txawv nrog kev xav, qhov uas cov lus hais txog kev xav thiab kev xav zoo li yuav cuam tshuam peb txoj kev tshawb nrhiav kev paub; hloov peb ntawm 'qhov tseeb