Wednesday, November 11, 2015

Oracle interview Questions

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Q:Compare and contrast TRUNCATE and DELETE for a table 
A:Both the truncate and delete command have the desired outcome of getting rid of all the rows in a table. The difference between the two is that the truncate command is a DDL operation and just moves the high water mark and produces few rollback data. The delete command, on the other hand, is a DML operation, which will produce rollback data and thus take longer to complete.  

Q:Explain the difference between $ORACLE_HOME and $ORACLE_BASE. 
A:ORACLE_BASE is the root directory for oracle. ORACLE_HOME located beneath ORACLE_BASE is where the oracle products reside.  

Q:What command would you use to encrypt a PL/SQL application? 
A:WRAP  

Q:How would you determine what sessions are connected and what resources they are waiting for? 
A:v$session,v$session_wait  

Q:What view would you use to determine free space in a tablespace? 
A:dba_free_space  

Q:Describe the difference between a procedure, function? 
A:A function must return a value while a procedure doesn\'t have to.   

Q:How can you find within a PL/SQL block, if a cursor is open? 
A:Use the %ISOPEN cursor status variable  

Q:What is the fastest query method for a table 
A:Fetch by rowid   

Q:How can you call a PL/SQL procedure from SQL? 
A:use of the EXECUTE (short form EXEC) command  

Q:How you will avoid duplicating records in a query? 
A:using DISTINCT keyword.  

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