On Wed, May 26, 2010 at 4:47 AM, Machiel Richards <machielr@rdc.co.za> wrote:
Good day all
Maybe someone could help me out from a resource point of view or even from an experience point of view.
I have been a dba for only a short while now and the training I did was not as intensive as you would get in cases like Oracle for instance.
I am currently involved in a project for one of the clients where they are busy consolidating and migrating some of their systems.
One of the tasks I need to do is to look at some of the queries that are quite lengthy and running for long periods, and then determine whether there are any indexes that should be added, etc...
I know I can use the explain option to see what the query time will be as well as some other info, however from experience point of view this does not mean much to me yet.
Can someone direct me to some info or assist regarding the following:
·What does the explain output mean and how to interpret the output to determine how queries can be optimised.
·Is there a guideline in terms of when / where indexes should be added or will be beneficial? How do I determine of the query needs and index or not.
As a VERY rough rule of thumb, any column that appears in a where clause or is used in a join should be indexed.
