Different Stages of an SQL statement - Optimizer

An SQL statement passes through 4 stages.  They are, Parse, bind, execute and fetch.

•          Parse:

o   Searches for identical statement in the MEMORY,

o   Checks for the syntax, object name and privileges,

o   Locks objects used during parse and

o   Create and store the execution plan.

•          Bind:

o   Obtains the values for the any host variables [& or &&],

•          Execute:

o   Process the statement, and

•          Fetch:

   o   Return rows to the user process.

The optimizer of the server determines the most efficient way to run a SQL statement. This is an important step in the processing of any data manipulation language (DM(Q)L) statement: SELECT, INSERT, UPDATE, MERGE, or DELETE.