Dab tsi yog coalesce muaj nuj nqi hauv Teradata?
Dab tsi yog coalesce muaj nuj nqi hauv Teradata?

Video: Dab tsi yog coalesce muaj nuj nqi hauv Teradata?

Video: Dab tsi yog coalesce muaj nuj nqi hauv Teradata?
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COALESCE yog siv los xyuas seb qhov kev sib cav yog NULL, yog tias nws yog NULL ces nws yuav siv tus nqi qub. Nws yuav kuaj rau TSIS NULL qhov tseem ceeb hauv cov npe thiab nws yuav rov qab thawj tus nqi TSIS TAU.

Ib yam li ntawd, txoj haujlwm coalesce yog dab tsi?

SQL ntawv Coalesce muaj nuj nqi . Lub SQL Coalesce thiab IsNull muaj nuj nqi yog siv los lis NULL qhov tseem ceeb. Lub SQL Coalesce muaj nuj nqi ntsuas cov lus sib cav nyob rau hauv kev txiav txim thiab ib txwm rov qab thawj tus nqi uas tsis yog null los ntawm daim ntawv teev kev sib cav.

Tsis tas li ntawd, dab tsi tsim nyog hauv Teradata? QUALIFY . ib qho kev taw qhia rau ib nqe lus uas muaj cai uas, zoo ib yam li HAVING, ntxiv cov lim kab los ntawm ib qho twg. Qhov sib txawv loj ntawm QUALIFY thiab HAVING yog qhov ntawd nrog QUALIFY kev lim dej yog raws li qhov tshwm sim ntawm kev ua ntau yam kev txiav txim analytical functions ntawm cov ntaub ntawv.

Raws li, Oreplace muaj nuj nqi hauv Teradata yog dab tsi?

Oreplace hauv Teradata yog siv rau hloov txhua qhov tshwm sim ntawm cov hlua khi nrog cov hlua tshiab hauv Teradata . Oreplace feem ntau yog siv los ua hloov tshem tawm ib feem ntawm ib txoj hlua.

Dab tsi yog cam khwb cia muaj nuj nqi hauv Teradata?

Teradata CAST muaj nuj nqi Piv txwv Cov CAST muaj nuj nqi yuav hloov hom kab lus lossis ib qho kev qhia rau lwm hom ntaub ntawv sib xws. Piv txwv li, xav txog cov piv txwv ntawm kev siv ntawm CAST muaj nuj nqi : xaiv pov tseg ('123456' as INT) as col1; col1 123456. Qhov tshwm sim yog tus nqi hloov dua siab tshiab.

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