The EXPLAIN command is a powerful tool provided with the Teradata database. It is designed to provide an English explanation of what steps the AMP must complete to satisfy the SQL request. The EXPLAIN is based on the PE's execution plan.
The
Parsing Engine (PE) does the optimization of the submitted SQL, the creation of
the AMP steps and the dispatch to any AMP involved in accessing the data. The
EXPLAIN is an SQL modifier; it modifies the way the SQL operates.