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Oracle SQL Tuning - Oracle Execution Plans for Beginners

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Text Comments (8)
content not clear
Stefano Priola (2 years ago)
explain plan for select ename,dname from emp natural join dept; select * from table(dbms_xplan.display);
Sasidhar Thiriveedhi (3 years ago)
The video is great. However the resolution of the content is not clear. Can you please publish the scripts ?
Hooah Grom (3 years ago)
low video quality:/ Should be banned from YT.
ashwani mishra (8 months ago)
Hooah Grom maa chuda
JavaEnthusiastic (3 years ago)
low video quality. Can't see anything clearly.
necraduq (3 years ago)
But by adding the hint to gather table statistics, it will run the query as if the actual statistics are updated. But if the statistics are not updated, then the optimizer could use the plan displayed by "explain plan for". What you encourage here is to run each query with "gather statistics", which could be useful, but also it might not be in the case of large tables. So, if the optimizer will look at old (stale) statistics, it will not choose the same plan as you proved. Also, "that is NOT all there is to SQL tuning". Tuning SQL is not about updating statistics or only about it. You can improve the performance of a query by updating statistics, but you also can make the performance much worse by updating statistics. On another note: what about the time it takes to gather statistics? How do you factor that in to the execution time of the query?
Akash Mishra (3 years ago)
useful!!! Thanks a lot

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