行业动态

Iroducio

Oracle daabase is widely used i he idusry for is reliabiliy ad scalabiliy. However, uforesee eves such as sysem crashes, huma errors, or aural disasers ca resul i daa loss. I such cases, he abiliy o recover daa becomes crucial. I his aricle, we will discuss how o recover able daa i Oracle usig SQL saemes.。

Udersadig Oracle Recovery

Oracle provides various mehods for daa recovery, icludig backup ad recovery, poi-i-ime recovery, ad media recovery. I his aricle, we will focus o recoverig able daa usig SQL saemes. This mehod is useful whe oly a small amou of daa eeds o be recovered or whe he backup is o available.。

Recoverig Table Daa Usig SQL

The firs sep i recoverig able daa is o ideify he poi i ime whe he daa was los. This ca be doe usig he Oracle Flashback Query feaure, which allows us o query he daa as i exised a a specific ime. For example, he followig SQL saeme rerieves all he daa from he "employees" able as i exised 30 miues ago:。

SELECT FROM employees AS OF TIMESTAMP (SYSDATE - (30/1440));。

If we kow he exac ime whe he daa was los, we ca use he followig SQL saeme o rerieve he daa from he redo log files:。

SELECT FROM employees LOGMIER WHERE SC BETWEE sar_sc AD ed_sc;。

The "sar_sc" ad "ed_sc" parameers ca be obaied from he aler log file or by queryig he V$LOGMR_COTETS view.。

Resorig Daa o he Table

Oce we have rerieved he los daa, we ca resore i o he able usig he followig SQL saeme:。

ISERT ITO employees SELECT FROM employees_bkp WHERE emp_id OT I (SELECT emp_id FROM employees);。

This saeme isers all he records from he backup able "employees_bkp" ha are o already prese i he "employees" able.。

Coclusio

Recoverig able daa i Oracle usig SQL saemes is a quick ad efficie mehod for resorig los or corruped daa. I is impora o regularly backup he daabase o miimize he risk of daa loss ad o esure ha he backup is readily available whe eeded.。

Tags: Oracle, daa recovery, SQL, able daa。