ANSI SQL 92 SYNTAX OUTER JOIN PERFORMANCE ISSUE

Question

Good Morning
Could anyone explain why the excution time for these two (ment to be identical)
queries run so differently.
oracle syntax execution time 1.06 seconds
select COUNT(*) from
PL_EVENT_VIEW pev,
PL_EVENT_STAFF_VIEW pesv
WHERE pev.EVENT_ID=PESV.EVENT_ID(+)
AND pev.WEEKS=PESV.WEEK_NUM(+)
AND pev.event_id=2520
ansi sql 92 syntax execution time 7.05 seconds
select COUNT(*) from
PL_EVENT_VIEW pev
LEFT JOIN PL_EVENT_STAFF_VIEW pesv
ON (pev.EVENT_ID=PESV.EVENT_ID
AND pev.WEEKS=PESV.WEEK_NUM)
WHERE pev.event_id=2520
Thanks
David Hills

Answer 1

BTW Oracle outer join operator (+) and ANSI SQL OUTER JOIN syntax are NOT equivalent. Consider following:
DROP TABLE T1;
CREATE TABLE T1 (C1 NUMBER);
DROP TABLE T2;
CREATE TABLE T2 (C2 NUMBER);
DROP TABLE T3;
CREATE TABLE T3 (C3 NUMBER);
-- Following SELECT works:
SELECT COUNT(*)
     FROM T1, T2, T3
     WHERE C2 = C1
          AND C3(+) = C1
COUNT(*)
0
-- But:
SELECT COUNT(*)
     FROM T1, T2, T3
     WHERE C2 = C1
          AND C3(+) = C1
          AND C3(+) = C2
AND C3(+) = C1
ERROR at line 4:
ORA-01417: a table may be outer joined to at most one other table
-- However with ANSI syntax:
SELECT COUNT(*)
     FROM T1
     JOIN T2 ON (C2 = C1)
     LEFT JOIN T3 ON (C3 = C1 AND C3 = C2)
COUNT(*)
0