Dab tsi yog timestamp hauv kev lag luam?
Dab tsi yog timestamp hauv kev lag luam?

Video: Dab tsi yog timestamp hauv kev lag luam?

Video: Dab tsi yog timestamp hauv kev lag luam?
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Anonim

Daim ntawv teev sijhawm yog tus cim tshwj xeeb tsim los ntawm DBMS los txheeb xyuas cov txheeb ze pib lub sijhawm ntawm a kev pauv nyiaj . Feem ntau, daim ntawv teev sijhawm tus nqi raug muab tso rau hauv qhov kev txiav txim uas kev lag luam raug xa mus rau qhov system. Yog li ntawd, a daim ntawv teev sijhawm tuaj yeem xav tias yog tus kev pauv nyiaj pib lub sij hawm.

Yog li ntawd, dab tsi yog timestamp raws tu qauv?

Daim ntawv teev sijhawm - raws tu qauv Cov daim ntawv teev sijhawm - raws algorithm siv a daim ntawv teev sijhawm los serialize qhov kev ua ntawm concurrent muas. Qhov no raws tu qauv xyuas kom meej tias txhua qhov kev tsis sib haum xeeb nyeem thiab sau cov haujlwm raug ua tiav hauv daim ntawv teev sijhawm xaj. Cov raws tu qauv siv System Time lossis Logical Count li a Daim ntawv teev sijhawm.

Tsis tas li ntawd, kev sib pauv hloov pauv yog dab tsi? Concurrent kev ua tiav ntawm database kev lag luam nyob rau hauv ib tug multi-user system txhais tau hais tias ib tug naj npawb ntawm cov neeg siv tau siv tib lub database nyob rau tib lub sij hawm. Concurrency kev tswj hwm yog xav tau txhawm rau kom tsis txhob muaj qhov tsis sib xws hauv cov ntaub ntawv.

Yog li ntawd, lub sij hawm xaj xaj ua haujlwm li cas?

Cov Timetamp Ordering raws tu qauv yog siv rau xaj kev pauv hloov raws li lawv Daim ntawv teev sijhawm . Txhawm rau txiav txim siab daim ntawv teev sijhawm ntawm kev ua lag luam, cov txheej txheem no siv lub sijhawm los yog cov khoom siv logic. Cov txheej txheem xauv raws li kev cai yog siv los tswj cov xaj nruab nrab ntawm kev tsis sib haum xeeb ntawm cov kev sib pauv thaum lub sijhawm ua tiav.

Yuav ua li cas sau lub sij hawm nyob rau hauv ib tug database?

Thaum koj ntxig a TIMESTAMP tus nqi rau hauv ib lub rooj, MySQL hloov nws los ntawm koj qhov kev sib txuas lub sijhawm rau UTC rau khaws cia. Thaum koj nug a TIMESTAMP tus nqi, MySQL converts tus nqi UTC rov qab rau koj qhov kev sib txuas lub sijhawm. Nco ntsoov tias qhov kev hloov pauv no ua tsis siv qhov chaw rau lwm yam ntaub ntawv ntawm lub cev xws li DATETIME.

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