What is explain ?

Explain Command in Teradata provides an "ENGLISH" translation of the steps choosen by the optimizer to execute an SQL statement.This is used to analyze all joins and complex queries.


 The following is an example:-

EXPLAIN

select last_name,first_name FROM employees;


The EXPLAIN parses the SQL statement but does not execute it.

This provides the designer with an "execution stratergy".

The execution stratergy provides what an optimizer does but not why it choses them.


when you run a query with the EXPLAIN command, it would NOT return any result data set, as mentioned, it just returns the explanation on how the results

would be  returned, in case the query runs.