Well, it's not aliases themselves, but the practice of using
aliases as prefixes, when referring to columns:
SELECTt1.col1, t1.col2, t2.col1
FROM table1 t1, table2 t2
WHERE t1.col2 = t2.col2
that's what saves time when parsing: this way you tell the
parser which table column list to look
Consider
SQL select deptno from emp,
dept; select deptno from emp,
dept * ERROR at line 1:
ORA-00918: column ambiguously defined
The
column deptno would be checked against one of the tables and would be found
to
be
valid, but the checking cannot stop there. The other table must also
