10) Qhov twg hauv qab no tsis yog kev ua haujlwm sib sau ua ke? Kev piav qhia: Kev sib sau ua ke yog siv los ua kev suav ntawm ntau qhov txiaj ntsig thiab xa rov qab cov zis hauv ib tus nqi. … COUNT, SUM, thiab MAX yog tag nrho cov haujlwm ua ke. COMPUTE tsis yog kev sib sau ua ke.
Yuav ua li cas aggregate siv tau?
Tshawb nrhiav: Cov haujlwm sib sau suav suav ib tus nqi los ntawm ntau kab. … Yog hais tias koj siv ib tug aggregate muaj nuj nqi nyob rau hauv koj cov lus nug ces tag nrho cov kab lus kab lus yuav tsum yog ib tug aggregate muaj nuj nqi, ib tug qhia nyob rau hauv lub GROUP BY clause los yog ib tug tas li qhia. Cov haujlwm sib sau ua ke tsuas yog siv tau hauv xaiv thiab HAVING clause
Dab tsi yog 5 lub luag haujlwm sib sau ua ke?
Muaj tsib lub luag haujlwm sib sau ua ke, uas yog: MIN, MAX, COUNT, SUM, thiab AVG.
Qhov twg hauv qab no yog kev sib sau ua ke?
Introduction to SQL aggregate functions
Cov hauv qab no yog cov feem ntau siv SQL aggregate functions: AVG – xam qhov nruab nrab ntawm ib pawg ntawm cov nqi. COUNT – suav kab hauv ib lub rooj los yog saib. MIN – tau txais tus nqi tsawg kawg nkaus hauv cov nqi.
Dab tsi yog qhov tsis sib sau ua ke?
Aggregate functions ua haujlwm ntawm ntau cov ntaub ntawv thiab tsim cov ntsiab lus, ua haujlwm nrog GROUP BY qhov tsis sib sau ua haujlwm ua haujlwm ntawm txhua cov ntaub ntawv ntawm nws tus kheej. Muaj ntau lub zog ua haujlwm hauv SQL los ua ntau yam kev suav ntawm cov ntaub ntawv.
