Cov kev ua ntawm kev tsim ib lub rooj hauv SQL - Tsim Cov Lus

Ua hauj lwm nrog databases yog hais txog kev hloov cov ntxhuav thiab cov ntaub ntawv muaj nyob hauv lawv. Tab sis ua ntej pib qhov kev txiav txim, lub rooj yuav tsum yog tsim. Kom automate txoj kev no, muaj ib qho tshwj xeeb SQL muaj nuj nqi hu ua "CREATE TABLE".

Thawj qhov!

Ua ntej koj yuav nrog cov txheej txheem ntawm kev tsim cov lus siv MS SQL hais kom ua "CREATE COV LUS", nws tsim nyog nyob rau ntawm yam koj yuav tsum paub ua ntej siv cov kev ua.

Ua ntej tshaj plaws, koj yuav tsum tuaj nrog lub npe rau lub rooj - nws yuav tsum yog txawv, zoo ib yam nrog lwm tus, nyob hauv tus database, thiab ua raws li ntau cov cai. Lub npe yuav tsum pib ntawm tsab ntawv (tsawg), tom qab uas cov ntawv, cov zauv thiab cov cim hauv qab no tuaj yeem ua raws nraim, thiab cov kab lus uas tau tshwm sim yuav tsum tsis yog lo lus tseg. Qhov ntev ntawm lub rooj sib tw yuav tsis pub dhau 18 cim.

Tom qab txhais lub npe, koj tsimnyog tsim tus qauv: xav txog cov npe ntawm txhua tus, xav txog cov ntaub ntawv siv nyob hauv lawv, thiab yuav tsum teb cov lus teb li cas. Ntawm no koj yuav tsum txiav txim siab tam sim ntawd rau thaj chaw ntawm sab nraud thiab thawj tus yuam sij, nrog rau cov kev txwv ntawm cov ntaub ntawv.

Tshuav tshooj ntawm lub rooj tuaj yeem yooj yim kho, yog li ntawm theem ntawm kev tsim rooj, lawv muaj peev xwm raug xav los ntawm tsis tag.

Syntax

Thaum tsim cov qauv ntawm lub rooj, koj tuaj yeem npaj mus tsim nws. Ua li no nws yog qhov yooj yim heev, siv SQL Function "CREATE COV LUS". Nyob hauv nws, tus neeg siv yuav tsum tau qhia kom paub cov lus teev npe thiab daim ntawv teev lus sau ua ke, qhia meej txog hom thiab npe rau txhua tus. Lub syntax ntawm lub Function yog raws li nram no:

CREATE Table table_name
({Column_name datatype [DEFAULT qhia] [column_constraint] ... | table_constraint}
[, {Column_name datatype [DEFAULT qhia] [column_constraint] ... | Table_constraint}] ...)

Cov kev sib cav uas siv rau hauv kev tsim kho ntawm kev ua haujlwm txhais tau li cas hauv qab no:

• Table_name - lub npe lub npe
• Column_name yog lub npe ntawm kem
• Datatype yog hom ntaub ntawv siv hauv daim teb no
• DEFAULT yog qhov qhia siv nyob rau hauv lub neej ntawd.

Nws tseem tuaj yeem siv ob nqe lus ntau ntxiv:

• Colum_constraint - sab tsis
• Table_constraint - cov lus tsis

Nyob rau ntawm lawv, tus neeg siv yuav tuaj yeem qhia meej txog cov kev txwv los yog cov kev ua rau kev sau daim ntawv.

Nta ntawm kev tsim cov ntxhuav

Thaum sau cov lus nug nrog SQL muaj nuj nqi "CREATE COV LUS", qee zaus koj yuav tsum teem caij rau cov kev cai sau teb. Ua li no, ntxiv cov cim tshwj xeeb ntawm qhov kev ua haujlwm uas txhais tau ib los yog lwm qhov ntawm cov xwm txheej.

Los txiav txim siab seb tus nqi npliag tau nyob hauv xov tooj ntawm tes, tom qab qhia meej lub npe thiab hom ntawm lub kem, ib qho ntawm cov ntsiab lus hauv qab no yuav tsum yog sau: NULL (tuaj yeem yog qhov tseem ceeb) lossis TSIS TAU (daim teb yuav tsum tau ua).

Thaum tsim ib lub rooj rau feem ntau, nws yuav tsum muab tag nrho txhua tus nkag mus kom tsis txhob muaj ob yam sib luag. Rau qhov no, tus lej feem ntau siv. Thiab, kom tsis txhob yuam kom tus neeg siv cov xov tooj dhau los hauv lub rooj, nyob hauv qhov ua "CREATE COV LUS" nws txaus los qhia kom meej ntawm kem ntawm cov thawj qhov tseem ceeb los ntawm kev sau lo lus tseem ceeb "Qhov tseem ceeb" tom qab teb. Feem ntau, nws yog thawj qhov tseem ceeb uas txuas cov ntxhuav rau ib leeg.

Txhawm rau muab qhov txuas mus rau lub Koom Haum Me Nyuam Yaus, qhov cuab yeej txawv teb chaws "FOREIGN KEY" siv. Los ntawm specifying cov cuab yeej no rau ib kem, koj tuaj yeem xyuas kom meej tias cov lus teb no muaj nqi uas sib dhos ntawm cov neeg nyob hauv kab ntawv tseem ceeb ntawm tib lub los yog lwm lub rooj. Nyob rau hauv txoj kev no, koj tuaj yeem xyuas kom meej tias cov ntaub ntawv no zoo ib yam.

Txhawm rau kom ua raws li cov txheej txheem uas tau muab teev tseg, siv cov yeeb yam hnyav. Nws sau kawg hauv daim ntawv teev cov lus sib tham rau qhov kev ua haujlwm thiab muaj kev qhia ua kom pom tseeb li ib tus kheej parameter. Siv nws, koj tuaj yeem txwv cov npe ntawm qhov tseem ceeb, piv txwv li, siv cov tsiaj ntawv "M" thiab "F" hauv teb ntawm lub rooj "Gender".

Ntxiv rau qhov hais, SQL muaj nuj nqi "CREATE COV LUS" muaj ntau ntau yam cwj pwm, tab sis lawv siv rau hauv kev xyaum ntau dua.

Piv txwv

Yuav kom nkag siab lub hauv paus ntsiab lus ntawm qhov kev ua haujlwm, nws yog qhov zoo tsim nyog rau hauv kev xyaum ua li cas CREATE COV LUS (SQL) ua haujlwm. Cov piv txwv hauv qab no tsim cov lus qhia hauv daim duab:

TSIM TXHEEJ TXHEEM
(ID CHAR (10) TSIS TXHOB XYUAS Qib siab,
Custom_name CHAR (20),
Custom_address CHAR (30),
Custom_city CHAR (20),
Custom_Country CHAR (20),
ArcDate CHAR (20))

Raws li koj tau pom, tus parameter ntawm qhov tsis tau ntawm tus nqi hauv cov xovtooj (NULL) yuav raug rho tawm, vim nws yog siv los ntawm lub neej ntawd.