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Oracle DBA Interview Questions

Q   |   QA

group by is used when we use aggregate functions on the columns in a query the other columns should be in group by query
select empno,ename,sum(sal) from emp group by empno,ename
Order by is used to sort values either in ascending or descending order

Crosscheck command


By running $ORACLE_HOME/rdbms/admin/spcreate.sql script

► Run a TOP command in Unix to see CPU usage (identify CPU killer processes)
► Run VMSTAT, SAR, and PRSTAT command to get more information on CPU and memory usage and possible blocking
► Run STATSPACK report to identify:
2. RESOURCE intensive SQL statements
► See if STATISTICS on affected tables needs to be re-generated
► IF poorly written statements are culprit, run a EXPLAIN PLAN on these statements and see whether new index or use of HINT brings the cost of SQL down.

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