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Video: Dab tsi yog kev siv substring hauv SQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
SQL ntawv Server SUBSTRING () ua haujlwm saib xyuas
Cov SUBSTRING () rho tawm a substring nrog ib tug ntev ntev pib los ntawm ib qho chaw nyob rau hauv ib txoj hlua input. SUBSTRING (input_string, pib, ntev); Hauv no syntax: input_string tuaj yeem ua tus cim, binary, ntawv nyeem, ntext, lossis cov duab qhia.
Tib neeg kuj nug, peb puas tuaj yeem siv substring nyob qhov twg?
Cov SUBSTRING SQL muaj nuj nqi tseem ceeb heev thaum koj xav kom paub tseeb tias txoj hlua qhov tseem ceeb rov qab los ntawm cov lus nug yuav raug txwv rau qee qhov ntev. Hauv qhov piv txwv hauv qab no, siv 'thawj lub npe' kem, ob lub cim kawg tau sib phim nrog lo lus 'on' siv SQL SUBSTRING ua haujlwm nyob rau qhov twg lus.
Tsis tas li ntawd, SQL txoj haujlwm yog dab tsi? SQL neeg rau zaub mov RIGHT() muaj nuj nqi saib xyuas Lub RIGHT() muaj nuj nqi rho tawm tus naj npawb ntawm cov cim los ntawm sab xis ntawm tus cim tshwj xeeb txoj hlua . Piv txwv li, LEEJ TWG ('SQL Server', 6) rov qab Server. Hauv no syntax: Cov input_string tuaj yeem yog qhov tseeb txoj hlua , variable, los yog kab.
Ntawm no, kuv yuav ua li cas tso thawj 3 cim hauv SQL?
Nyob zoo Shanu, Koj tuaj yeem siv LEN() lossis LENGTH()(nyob rau hauv rooj plaub ntawm oracle sql ua ) muaj nuj nqi kom tau qhov ntev ntawm ib kab. SELECT LEN(column_name) NTAWM table_name; Thiab koj tuaj yeem siv SUBSTRING los yog SUBSTR() muaj nuj nqi mus tau thawj peb lub cim ntawm ib kab.
Yuav ua li cas koj txiav cov ntawv hauv SQL?
Yog tias muaj, koj muaj ob peb txoj kev xaiv:
- Koj tuaj yeem siv TRIM (lossis LTRIM lossis RTRIM) ua haujlwm kom tshem tawm qhov chaw lossis lwm cov cim ntawm sab laug lossis sab xis ntawm txoj hlua.
- Koj tuaj yeem siv LEFT muaj nuj nqi hauv SQL Server, lossis SUBSTR muaj nuj nqi hauv Oracle SQL, xa rov qab ib txoj hlua nrog cov cim tshwj xeeb los ntawm cov hlua loj dua.
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