Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

CHAPTER 10 ■ DATABASE TABLES 359
ops$tkyte@ORA10GR1> begin
2 for x in ( select empno from emp )
3 loop
4 for y in ( select emp.ename, a.street, a.city, a.state, a.zip
5 from emp, heap_addresses a
6 where emp.empno = a.empno
7 and emp.empno = x.empno )
8 loop
9 null;
10 end loop;
11 end loop;
12 end;
13 /
PL/SQL procedure successfully completed.
Here, we are just emulating a busy period and running the query some 45,000 times, once
for each EMPNO. If we run that for the HEAP_ADRESSES and IOT_ADDRESSES tables, TKPROF shows us
the following:
SELECT EMP.ENAME, A.STREET, A.CITY, A.STATE, A.ZIP
FROM EMP, HEAP_ADDRESSES A
WHERE EMP.EMPNO = A.EMPNO AND EMP.EMPNO = :B1
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 48244 7.66 7.42 0 0 0 0
Fetch 48244 6.29 6.56 0 483393 0 192976
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 96489 13.95 13.98 0 483393 0 192976
Rows Row Source Operation
------- ---------------------------------------------------
192976 NESTED LOOPS (cr=483393 pr=0 pw=0 time=5730335 us)
48244 TABLE ACCESS BY INDEX ROWID EMP (cr=144732 pr=0 pw=0 time=1594981 us)
48244 INDEX UNIQUE SCAN EMP_PK (cr=96488 pr=0 pw=0 time=926147 us)...
192976 TABLE ACCESS BY INDEX ROWID HEAP_ADDRESSES (cr=338661 pr=0 pw=0 time=...
192976 INDEX RANGE SCAN SYS_C008073 (cr=145685 pr=0 pw=0 time=1105135 us)...
********************************************************************************
SELECT EMP.ENAME, A.STREET, A.CITY, A.STATE, A.ZIP
FROM EMP, IOT_ADDRESSES A
WHERE EMP.EMPNO = A.EMPNO AND EMP.EMPNO = :B1
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 48244 8.17 8.81 0 0 0 0
Fetch 48244 4.31 4.12 0 292918 0 192976