Cov txheej txheem:
Video: Yuav ua li cas kuv suav ib varchar kab hauv SQL?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
SQL SERVER - Yuav ua li cas sau ib kab ntawv varchar
- Kauj Ruam 1: Cia kuv tsim ib lub rooj los qhia txog kev daws teeb meem.
- Kauj Ruam 2: Ntxig qee cov ntaub ntawv dummy los ua aggregate SUM ntawm kem ([Kab_varchar]).
- Kauj ruam 3: Xauj cov ntaub ntawv los ntawm lub rooj thiab xyuas cov datatypes.
- Kauj ruam 4: Raws li koj tuaj yeem pom muaj ',' (Comma) hauv ID no 4 hauv lub rooj.
- Kauj ruam 5:
Ib yam li ntawd, kuv yuav ua li cas thiaj li tau txais cov lej ntawm kab hauv SQL?
SUM() muaj nuj nqi rov qab tag nrho cov lej ntawm ib kab zauv
- COUNT() Syntax. SELECT COUNT(column_name) NTAWM table_name. Qhov twg mob;
- AVG() Syntax. SELECT AVG(column_name) NTAWM table_name. Qhov twg mob;
- SUM() Syntax. SELECT SUM(column_name) NTAWM table_name. Qhov twg mob;
Koj puas tuaj yeem suav hauv SQL? Cov SQL ntawv Server SUM () muaj nuj nqi yog ib tug aggregate muaj nuj nqi uas xam cov sum ntawm tag nrho los yog txawv qhov tseem ceeb hauv kev nthuav qhia. Hauv no syntax: DISTINCT qhia tus SUM () muaj nuj nqi los xam cov sum ntawm tus nqi sib txawv xwb. kev nthuav qhia yog ib qho kev qhia siv tau uas rov qab muaj pes tsawg lossis kwv yees tus nqi.
Ib qho tseem yuav nug, Kuv tuaj yeem suav lub sijhawm hauv varchar kem hauv SQL Server li cas?
Hauv blog no, cia peb saib yuav ua li cas sum tag nrho cov sij hawm tam sim no nyob rau hauv varchar kab hauv SQL server.
Peb yuav ua nws hauv ib lo lus nug tab sis muaj 4 kauj ruam hauv qhov ntawd.
- Hloov Timefield rau hnub tim.
- Hloov cov teev, feeb mus rau vib nas this hauv lub sijhawm hloov dua siab tshiab.
- Sau cov vib nas this.
- Hloov cov vib nas this rov mus rau teev hom.
Dab tsi yog varchar hauv SQL nrog piv txwv?
VARCHAR yog qhov ntev sib txawv txoj hlua hom ntaub ntawv, yog li nws tuav tsuas yog cov cim koj muab rau nws. VARCHAR siv 1 byte ib tus cim, + 2 bytes tuav cov ntaub ntawv ntev. Rau piv txwv , yog koj teev a VARCHAR (100) cov ntaub ntawv hom = 'Jen', ces nws yuav siv li 3 bytes (rau J, E, thiab N) ntxiv rau 2 bytes, lossis 5 bytes hauv tag nrho.
Pom zoo:
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