Nested joins in Teradata - response (2) by M.Saeed Khurram

Hi,
Nested joins are the most efficient join types used in Teradata. They are mostly useful with OLTP requests. 
In a nested join a row is selected from one table using an equality condition on PI or USI. and this single row is then joined with the one or more rows from the other table selected based on a PI, USI, or NUSI.
Raja has qouted a good simple example of Nested join, I would add that in this case EMP.NUM must be a PI or USI.