A qualifier that designates a specific object table is called a table designator. The clause that identifies the object tables also establishes the table designators for them.
For example, the object tables of an expression in a SELECT clause are named in the FROM clause that follows it:
SELECT CORZ.COLA, OWNY.MYTABLE.COLA FROM OWNX.MYTABLE CORZ, OWNY.MYTABLE
Table designators in the FROM clause are established as follows:
SELECT CORZ.COLA, MYTABLE.COLA FROM OWNX/MYTABLE CORZ, OWNY/MYTABLE
Two or more object tables can be instances of the same table. In this case, distinct correlation names must be used to unambiguously designate the particular instances of the table. In the following FROM clause, X and Y are defined to refer, respectively, to the first and second instances of the table EMPLOYEE:
SELECT * FROM EMPLOYEE X,EMPLOYEE Y