I-Oracle SQL iwulimi lokuhlela olunamandla olusetshenziselwa ukuphatha amasistimu okuphatha imininingwane egciniwe (RDBMS). Namuhla, sizocubungula ngokujulile umqondo othile - umyalo we-SQL Drop Index.
I-Index ku-SQL isetshenziselwa ukusheshisa ukubuyiswa kwemigqa ngokusebenzisa i-pointer. Kuyinto yesizindalwazi edalwe kuthebula elikhona ukuze kusheshiswe inqubo yokubuyisa imigqa. Nokho, nakuba kunenzuzo, kungase kube nezidingo zokwehlisa inkomba. Isitatimende se-SQL DROP INDEX sisetshenziselwa ukwenza lokhu futhi sisiza ekususeni inkomba kuthebula.
Umyalo we-SQL DROP INDEX
Umyalo we-SQL DROP INDEX uwumsebenzi we-DDL (Data Definition Language) osetshenziselwa ukumaka inkomba ukuze isuswe ngokukhipha inkomba yento eyodwa noma ngaphezulu engadingekile kusichazamazwi sesizindalwazi. Lokhu kungaba yinzuzo ukukhulula isikhala esithile ohlelweni noma lapho inkomba ingasadingeki. I-syntax ye-SQL yalokhu ilula kakhulu:
DROP INDEX index_name;
Lapho elithi 'index_name' kuyigama lenkomba ohlose ukuyiyeka.
Sicela ukhumbule, ngenkathi usebenzisa isitatimende se-DROP INDEX, cabanga ukuthi singaba nomthelela omubi ekusebenzeni kwe-SQL uma inkomba isetshenziswa kakhulu ekubuyiseni imibuzo. Ukuqonda uhlelo kanye nezidingo zalo kubalulekile ngenkathi ubhekene nezinkomba zokwehla.
Isinyathelo ngesinyathelo Ukwenziwa komyalo we-DROP INDEX
Ukuze siqonde kangcono, ake sidlule ekwenzeni isinyathelo ngesinyathelo sokudala, sisebenzisa bese silahla inkomba ku-Oracle SQL.
- Ake sicabange ukuthi sinetafula elibizwa ngokuthi 'Amakhasimende' elinekholomu 'ye-Custom_id' phakathi kwamanye. Isinyathelo sokuqala siwukwenza inkomba kule kholomu ye-'Customer_id' uma ingekho kakade. Umyalo walokhu uthi
DALA INDEX idx_customer
KUMAmakhasimende (Customer_id); - Manje, cabanga ukuthi imisebenzi eminingi yenziwa kusetshenziswa le nkomba. Kancane kancane, uhlelo luphawula ukuthi le nkomba ayisadingeki.
- Ukuze uwise inkomba, umyalo we-DROP INDEX usetshenziswa.
YEHLISA ISIHLOKO idx_customer;
Uma isikhishiwe, inkomba ethi 'idx_customer' izokwehliswa kuthebula elithi 'Amakhasimende' futhi isikhala esisetshenziswe yiyo sizokhishwa.
Ehlobene SQL Concepts
Ngaphandle kwesitatimende se-DROP INDEX, kuneminye imiyalo ye-DDL ku-SQL enomthelela ekuphatheni isizindalwazi ngempumelelo:
DALA INDEX: Lo myalo usetshenziselwa ukwakha inkomba kumakholomu ethebula.
NGESINYE ISIKHOMBISI: Isitatimende se-ALTER INDEX silungisa inkomba ekhona noma izici zayo. Ushintsho lungaba ukwakha kabusha, ukuqamba kabusha, ukunika amandla noma ukukhubaza inkomba.
Ukusebenza kwe-SQL nokuphathwa kwesikhala kungaba isici esiyinselele sokuphatha isizindalwazi. Ukusetshenziswa ngempumelelo kwemiyalo ye-DDL efana ne-DROP INDEX, uma kucatshangelwa izidingo zesistimu, kungasiza kakhulu ekufinyeleleni ukusebenza kahle. Hlala ukhumbula ukuhlola kabili ukusetshenziswa kwale miyalo njengoba ingaba nomthelela omkhulu kusizindalwazi.