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Oracle® Database SQL Language Reference
11g Release 1 (11.1)

B28286-07
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Logical Conditions

A logical condition combines the results of two component conditions to produce a single result based on them or to invert the result of a single condition. Table 7-4 lists logical conditions.

Table 7-4 Logical Conditions

Type of Condition Operation Examples
NOT 

Returns TRUE if the following condition is FALSE. Returns FALSE if it is TRUE. If it is UNKNOWN, then it remains UNKNOWN.

SELECT *
  FROM employees
  WHERE NOT (job_id IS NULL)
  ORDER BY employee_id;
SELECT *
  FROM employees
  WHERE NOT 
  (salary BETWEEN 1000 AND 2000)
  ORDER BY employee_id;
AND 

Returns TRUE if both component conditions are TRUE. Returns FALSE if either is FALSE. Otherwise returns UNKNOWN.

SELECT *
  FROM employees
  WHERE job_id = 'PU_CLERK'
  AND department_id = 30
  ORDER BY employee_id;
OR 

Returns TRUE if either component condition is TRUE. Returns FALSE if both are FALSE. Otherwise returns UNKNOWN.

SELECT *
  FROM employees
  WHERE job_id = 'PU_CLERK'
  OR department_id = 10
  ORDER BY employee_id;

Table 7-5 shows the result of applying the NOT condition to an expression.

Table 7-5 NOT Truth Table

-- TRUE FALSE UNKNOWN

NOT

FALSE

TRUE

UNKNOWN


Table 7-6 shows the results of combining the AND condition to two expressions.

Table 7-6 AND Truth Table

AND TRUE FALSE UNKNOWN

TRUE

TRUE

FALSE

UNKNOWN

FALSE

FALSE

FALSE

FALSE

UNKNOWN

UNKNOWN

FALSE

UNKNOWN


For example, in the WHERE clause of the following SELECT statement, the AND logical condition is used to ensure that only those hired before 1989 and earning more than $2500 a month are returned:

SELECT * FROM employees
WHERE hire_date < TO_DATE('01-JAN-1989', 'DD-MON-YYYY')
  AND salary > 2500
  ORDER BY employee_id;

Table 7-7 shows the results of applying OR to two expressions.

Table 7-7 OR Truth Table

OR TRUE FALSE UNKNOWN

TRUE

TRUE

TRUE

TRUE

FALSE

TRUE

FALSE

UNKNOWN

UNKNOWN

TRUE

UNKNOWN

UNKNOWN


For example, the following query returns employees who have a 40% commission rate or a salary greater than $20,000:

SELECT employee_id FROM employees
   WHERE commission_pct = .4 OR salary > 20000
   ORDER BY employee_id;