Video: Dab tsi yog hom ntaub ntawv rau email hauv SQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
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Tsis tas li, hom ntaub ntawv twg yog email chaw nyob?
VARCHAR yog qhov zoo tshaj plaws hom ntaub ntawv siv tau rau email chaw nyob raws li Emails txawv ntau ntawm qhov ntev. NVARCHAR kuj yog lwm txoj hauv kev tab sis kuv xav kom nws siv yog tias tus email chaw nyob muaj cov kab txuas txuas ntxiv thiab khaws cia hauv nco ntsoov tias nws yuav tsum tau muab ob npaug ntawm qhov chaw cia li piv rau VARCHAR.
Tom qab ntawd, lo lus nug yog, hom SQL commands yog dab tsi? Muaj tsib hom SQL Commands uas tuaj yeem faib ua:
- DDL (Data txhais lus).
- DML (Data Manipulation Language).
- DQL (Data Query Language).
- DCL (Data Control Language).
- TCL (Kev Tswj Kev Lag Luam).
Tsis tas li ntawd, datatype hauv SQL yog dab tsi?
A hom ntaub ntawv yog tus cwj pwm uas qhia txog hom ntaub ntawv uas cov khoom muaj peev xwm tuav tau: integer data, character data, monetary data, date and time data, binary strings, and so on. SQL ntawv Server muab cov txheej txheem hom ntaub ntawv uas txhais tag nrho cov hom ntaub ntawv uas tuaj yeem siv nrog SQL ntawv Server.
Dab tsi yog txoj hlua cov ntaub ntawv hom hauv SQL?
Hauv sql ua , txoj hlua cov ntaub ntawv hom yog siv los khaws txhua yam cov ntaub ntawv hauv rooj. Hauv txoj hlua cov ntaub ntawv hom , peb muaj kev xaiv tso cai rau cov neeg siv khaws cia ntev ntawm cov cim lossis ntev ntev cov ntaub ntawv raws li lawv cov kev xav tau.
Pom zoo:
Cov ntaub ntawv hom thiab cov qauv ntaub ntawv yog dab tsi?
Cov qauv ntaub ntawv yog ib txoj hauv kev piav qhia txog ib txoj hauv kev los npaj cov ntaub ntawv kom ua haujlwm andalogrithms tuaj yeem siv tau yooj yim dua. Ib hom ntaub ntawv piav qhia txog cov ntaub ntawv uas txhua tus sib koom ua ke. Piv txwv li tus lej cov ntaub ntawv hom piav qhia txhua tus lej uas lub khoos phis tawj tuaj yeem ua tau
Dab tsi yog hom ntaub ntawv thiab cov ntaub ntawv sib txawv?
Qee cov ntaub ntawv muaj xws li cov lej, cov lej ntab, cov cim, cov hlua, thiab cov arrays. Lawv kuj tseem yuav yog hom tshwj xeeb, xws li hnub tim, timestamps, booleanvalues, thiab varchar (tus cwj pwm sib txawv) cov qauv
Dab tsi yog lub hom phiaj ntawm delimiters nyob rau hauv cov ntawv sau npe ob hom ntawv cov ntaub ntawv delimiters?
Cov ntaub ntawv delimited yog cov ntawv nyeem siv los khaws cov ntaub ntawv, uas txhua kab sawv cev rau ib phau ntawv, tuam txhab, lossis lwm yam, thiab txhua kab muaj cov teb sib cais los ntawm tus lej
Dab tsi yog hom ntawv cov ntaub ntawv hauv SQL Server?
Nws yog Non-Unicode loj sib txawv ntev lub cim cov ntaub ntawv hom, uas tuaj yeem khaws qhov siab tshaj plaws ntawm 2147483647 Cov Cim Tsis-Unicode (piv txwv li qhov muaj peev xwm cia siab tshaj plaws yog: 2GB). Version ntawm Sql Server nyob rau hauv uas nws tau qhia? Cov ntaub ntawv hom yog tam sim no los ntawm cov qub versions ntawm Sql Server
Hom ntaub ntawv twg ntawm Hadoop tso cai rau columnar cov ntaub ntawv cia hom?
Columnar ntaub ntawv tawm tswv yim (Parquet, RFile) Qhov tseeb hotness nyob rau hauv cov ntaub ntawv tawm tswv yim rau Hadoop iscolumnar cov ntaub ntawv cia. Yeej qhov no txhais tau hais tias tsis yog cia li khaws cov kab ntawm cov ntaub ntawv nyob ib sab rau ib leeg koj kuj khaws cov kab ntawv nyob ib sab. Yog li datasets tau muab faib ua ob qho tib si horizontally thiab vertically