Learning PostgreSQL 11 - Third Edition

The WHERE clause

In many cases, after the rows are taken from the input tables, they should be filtered. This is done via the WHERE clause. The filtering condition is specified after the WHERE keyword. The condition is a SQL expression that returns a Boolean value. That's why the syntax of the WHERE condition is the same as in the expressions in the SELECT-list. This is specific to PostgreSQL. In other databases, it may not be possible to use Boolean values in the SELECT-list, which makes SQL conditions different from SQL expressions. In PostgreSQL, the difference is only in the data type of a returned value.

Simple examples of WHERE conditions are as follows:

SELECT * FROM car_portal_app.car_model WHERE make='Peugeot';SELECT * FROM car_portal_app.car ...