>>-+-expression--+- = ------+--expression------------+--------->< | | (1) | | | +- <> -----+ | | +- < ------+ | | +- > ------+ | | | (1) | | | +- <= -----+ | | | (1) | | | '- >= -----' | '-row-value-expression-- = --row-value-expression-'
A basic predicate compares two values or compares a set of values with another set of values.
When a single expression is specified on the left side of the operator, another expression must be specified on the right side. The data types of the corresponding expressions must be compatible. The value of the expression on the left side is compared with the value of the expression on the right side. If the value of either operand is null, the result of the predicate is unknown. Otherwise the result is either true or false.
When a row-value-expression is specified on the left side of the operator and another row-value-expression is specified on the right side of the operator, each row-value-expression must have the same number of value expressions. The data types of the corresponding expressions for each row-value-expression must be compatible. The value of each expression on the left side is compared with the value of its corresponding expression on the right side.
EMPNO='528671'
SALARY < 20000
PRSTAFF <> :VAR1
SALARY > (SELECT AVG(SALARY) FROM EMPLOYEE)