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Dab tsi yog kev koom nrog sab hauv hauv SQL?
Dab tsi yog kev koom nrog sab hauv hauv SQL?

Video: Dab tsi yog kev koom nrog sab hauv hauv SQL?

Video: Dab tsi yog kev koom nrog sab hauv hauv SQL?
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Dab tsi yog Inner Koom hauv SQL ? Cov PIB HAIV NEEG xaiv tag nrho cov kab los ntawm ob lub rooj koom nrog tsuav yog tias muaj kev sib tw ntawm cov kab. Ib SQL INNER JOIN yog tib yam li Koom clause, sib txuas kab los ntawm ob lossis ntau lub rooj.

Ua li no, ua li cas koj sau ib qho kev koom nrog hauv SQL?

SQL INNER JOIN lo lus tseem ceeb

  1. SELECT column_name(s) NTAWM table1. INNER JOIN rooj 2. ON table1.column_name = table2.column_name;
  2. Piv txwv. SELECT Orders. OrderID, Customers. CustomerName. Los ntawm Orders. INNER JOIN Cov Neeg Siv Khoom ON Orders. CustomerID = Customers. CustomerID;
  3. Piv txwv. SELECT Orders. OrderID, Customers. CustomerName, Shippers. ShipperName. NTAWM ((Orders.

Tsis tas li, dab tsi yog sab laug koom nrog hauv SQL? ( Sab hauv ) Koom : Rov qab cov ntaub ntawv uas muaj qhov sib xws hauv ob lub rooj. LEEJ TWG ( OUTER ) Koom : Rov qab tag nrho cov ntaub ntawv los ntawm sab laug rooj, thiab cov ntaub ntawv sib phim los ntawm lub rooj sab xis. Txoj cai ( OUTER ) Koom : Rov qab tag nrho cov ntaub ntawv los ntawm lub rooj sab xis, thiab cov ntaub ntawv sib tw los ntawm sab laug rooj.

Hauv qhov no, qhov sib txawv ntawm qhov sib koom sab hauv thiab sab nrauv yog dab tsi?

Ob leeg sab hauv thiab sab nrauv koom yog siv los muab cov kab ntawm ob lossis ntau lub rooj rau hauv ib qho txiaj ntsig. Qhov no yog ua tiav siv a koom mob. Cov koom xwm txheej qhia tias kab los ntawm txhua lub rooj sib phim rau ib leeg. Sab hauv koom tsis suav cov kab uas tsis sib xws; hos, sab nrauv koom suav nrog lawv.

Dab tsi yog kev koom nrog sab hauv thiab sab nraud koom nrog SQL nrog cov piv txwv?

Sab nrauv koom . Hauv SQL ntawv , a koom yog siv los sib piv thiab ua ke - lus koom - thiab xa cov kab tshwj xeeb ntawm cov ntaub ntawv los ntawm ob lossis ntau lub rooj hauv cov ntaub ntawv. Ib sab hauv koom nrhiav thiab xa cov ntaub ntawv sib txuam los ntawm cov ntxhuav, thaum ib sab nraud koom nrhiav thiab xa rov qab cov ntaub ntawv sib txuam thiab qee cov ntaub ntawv sib txawv ntawm cov ntxhuav.

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