FROM clause

The FROM clause is a mandatory clause in a SelectExpression. It specifies the tables (TableExpression) from which the other clauses of the query can access columns for use in expressions.

Syntax

FROM TableExpression [ , TableExpression ] *
SELECT Cities.city_id
FROM Cities
WHERE city_id < 5
-- other types of TableExpressions
SELECT TABLENAME, ISINDEX 
FROM SYS.SYSTABLES T, SYS.SYSCONGLOMERATES C
WHERE T.TABLEID = C.TABLEID
ORDER BY TABLENAME, ISINDEX;
-- force the join order
SELECT *
FROM Flights, FlightAvailability
WHERE FlightAvailability.flight_id = Flights.flight_id
AND FlightAvailability.segment_number = Flights.segment_number
AND Flights.flight_id < 'AA1115'
-- a TableExpression can be a joinOperation. Therefore
-- you can have multiple join operations in a FROM clause
SELECT COUNTRIES.COUNTRY, CITIES.CITY_NAME, FLIGHTS.DEST_AIRPORT
FROM COUNTRIES LEFT OUTER JOIN CITIES
ON COUNTRIES.COUNTRY_ISO_CODE = CITIES.COUNTRY_ISO_CODE
LEFT OUTER JOIN FLIGHTS
ON Cities.AIRPORT = FLIGHTS.DEST_AIRPORT;
Related concepts
Interaction with the dependency system
CREATE statements
DROP Statements
RENAME statements
SET statements
Related reference
ALTER TABLE statement
CALL (PROCEDURE)
CONSTRAINT clause
DECLARE GLOBAL TEMPORARY TABLE statement
DELETE statement
FOR UPDATE clause
GROUP BY clause
HAVING clause
INNER JOIN
INSERT statement
JOIN operation
LEFT OUTER JOIN
LOCK TABLE statement
ORDER BY clause
Query
RIGHT OUTER JOIN
ScalarSubquery
SelectExpression
SELECT statement
TableExpression
TableSubquery
UPDATE statement
VALUES expression
WHERE clause
WHERE CURRENT OF clause