Video: Peb puas tuaj yeem tsim qhov ntsuas ntawm kab virtual hauv Oracle?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Virtual kab tuaj yeem siv nyob rau hauv qhov chaw nyob clause ntawm UPDATE thiab DELETE nqe lus tab sis lawv ua tau 'tsis raug hloov kho los ntawm DML. Lawv ua tau siv los ua tus yuam sij muab faib hauv virtual kab raws li partitioning. Indexs tau raug tsim rau lawv. Raws li koj tej zaum yuav tau kwv yees, oracle yuav tsim muaj nuj nqi raws li indexes raws li peb tsim ntawm cov rooj qub.
Khaws qhov no hauv kev txiav txim siab, ntawm kab ntawv twg koj yuav tsum tsim qhov ntsuas hauv Oracle?
Indexs muab kev nkag tau sai rau cov ntaub ntawv rau kev ua haujlwm uas rov qab ib feem me me ntawm lub rooj kab . Feem ntau, koj yuav tsum tsim qhov Performance index ntawm ib kem hauv ib qho ntawm cov xwm txheej hauv qab no: Kab lus nug ntau zaus. Ib qho kev txwv kev ncaj ncees muaj nyob rau ntawm kab.
Tsis tas li ntawd, kuv puas tuaj yeem tsim qhov Performance index ntawm saib hauv Oracle? Indexing thiab Saib . Oracle SQL qauv ua tsis txhawb tsim indexes ntawm views . Yog koj xav tau qhov ntsuas cov ntaub ntawv uas nws cov ntsiab lus nyob rau hauv cov rooj sib txawv, koj tuaj yeem tsim cov ntaub ntawv khaws cia nyiam siv USER_DATASTORE khoom.
Ib yam li ntawd, dab tsi yog ib kem virtual hauv Oracle?
Taw qhia rau lub Oracle virtual kab A virtual kab yog lub rooj kem uas nws qhov tseem ceeb yog xam tau siv lwm yam kem qhov tseem ceeb, lossis lwm qhov kev txiav txim siab. Ntawm no yog cov syntax ntawm a virtual kab : 1. column_name [data_type] [GENERATED ALWAYS] AS (expression) [ VIRTUAL ]
Peb puas tuaj yeem tsim qhov ntsuas ntawm lub hauv paus tseem ceeb hauv Oracle?
Los ntawm default, lub CREATE INDEX nqe lus tsim ib tug btree qhov ntsuas . Thaum koj tsim ib lub rooj tshiab nrog a thawj tus yuam sij , Oracle cia li tsim ib qho tshiab qhov ntsuas rau cov thawj cov kab ke . Tsis zoo li lwm cov database systems, Oracle tsis tau tsim ib qhov ntsuas rau txawv teb chaws cov kab tseem ceeb.
Pom zoo:
Koj puas tuaj yeem tsim qhov ntsuas ntawm lub rooj sib txawv?
Tsim ib qho kev ntsuas ntawm lub rooj sib txawv tuaj yeem ua tiav hauv qhov kev tshaj tawm ntawm lub rooj sib txawv los ntawm kev txhais cov ntsiab lus tseem ceeb thiab tsim cov kev txwv tshwj xeeb. Koj tseem tuaj yeem tsim qhov sib npaug ntawm qhov ntsuas qhov ntsuas. Txhawm rau ua li ntawd, tsuas yog ntxiv cov lus khaws tseg cia
Peb puas tuaj yeem siv ob kab hauv kev faib los ntawm?
PARTITION LOS NTAWM ntau kab. PARTITION BY clause tuaj yeem siv los rhuav tshem qhov nruab nrab qhov rais los ntawm ntau cov ntaub ntawv cov ntsiab lus (kem). Piv txwv li, koj tuaj yeem suav cov hom phiaj nruab nrab ntawm lub caij nyoog thiab los ntawm lub teb chaws, lossis los ntawm lub xyoo daim ntawv qhia hnub (nrhiav los ntawm kab hnub)
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
Dab tsi yog qhov sib txawv ntawm qhov ntsuas qhov ntsuas thiab qhov ntsuas thib ob?
Primary index: nyob rau hauv ib tug sequentially order file, qhov Performance index uas nws search key qhia cov sequential order ntawm cov ntaub ntawv. Kuj hu ua clustering index. Secondary index: ib qho Performance index uas nws qhov tseem ceeb tshawb nrhiav qhia qhov kev txiav txim sib txawv ntawm qhov kev txiav txim ntawm cov ntaub ntawv. Kuj hu ua non-clustering index
Dab tsi yog qhov ntsuas qhov ntsuas qhov ntsuas qhov ntsuas?
Xav txog nws li no: rhiab heev yog ib qho kev ntsuas ntawm qhov hloov pauv ntawm lub koob yees duab qhov chaw saib uas tsim nyog raws li qhov muaj peev xwm tshawb pom, thiab qhov pib yog qhov ntau npaum li cas ntawm cov lus tsa suab yuav tsum tshwm sim txhawm rau txhawm rau ua rau lub tswb