WHERE clause

The WHERE clause specifies the conditions that records must meet to be retrieved. The WHERE clause contains conditions in the form:

WHERE expr1 rel_operator expr2

expr1 and expr2 can be field names, constant values, or expressions.

rel_operator is the relational operator that links the two expressions.

SELECT last_name,first_name FROM emp WHERE salary >= 20000

The WHERE clause can also use expressions such as these:

WHERE expr1 IS NULL
WHERE NOT expr2

Note  If you use fully qualified names in the SELECT (projection) list, you must also use fully qualified names in the related WHERE clause.