WHERE Clause Teradata

The previous "unconstrained" SELECT statement returned every row from the table. Since the Teradata database is most often used as a data warehouse, a table might contain millions of rows. So, it is wise to request only certain types of rows for return. By adding a WHERE clause to the SELECT, a constraint is established to potentially limit which rows are returned based on a TRUE comparison to specific criteria or set of conditions.

WHERE Clause

The following SELECT can be used to return the students with a (3.0) average or better from the Student table:

5 Rows returned

WHERE Clause

Without the WHERE clause, the AMPs return all of the rows in the table to the user. More and more Teradata user systems are getting to the point where they are storing billions of rows in a single table. There must be a very good reason for needing to see all of them. More simply put, you will always use a WHERE clause whenever you want to see only a portion of the rows in a table.

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