关于Oracle分页
Connected to Oracle9i Enterprise Edition Release 9.2.0.6.0
Connected as dev
SQL>
SQL> SET timing ON;
SQL> CREATE TABLE test_table AS
2 SELECT rownum x
3 FROM dual
4 START WITH rownum = 1
5 CONNECT BY rownum <= 1000000;
Table created
Executed in 4.125 seconds
SQL> --89991至90000行
SQL> --A方法
SQL> SELECT *
2 FROM (SELECT /*+ first_rows */
3 x, rownum num
4 FROM (SELECT x FROM test_table ORDER BY x DESC)
5 WHERE rownum <= 90000)
6 WHERE num >= 89991;
X NUM
---------- ----------
910010 89991
910009 89992
910008 89993
910007 89994
910006 89995
910005 89996
910004 89997
910003 89998
910002 89999
910001 90000
10 rows selected
Executed in 4.579 seconds
SQL> --B方法
SQL> SELECT *
2 FROM (SELECT x, rownum num FROM (SELECT x FROM test_table ORDER BY x DESC))
3 WHERE num BETWEEN 89991 AND 90000;
X NUM
---------- ----------
910010 89991
910009 89992
910008 89993
910007 89994
910006 89995
910005 89996
910004 89997
910003 89998
910002 89999
910001 90000
10 rows selected
Executed in 6.891 seconds
SQL> --1至10行
SQL> --A方法
SQL> SELECT *
2 FROM (SELECT /*+ first_rows */
3 x, rownum num
4 FROM (SELECT x FROM test_table ORDER BY x DESC)
5 WHERE rownum <= 10)
6 WHERE num >= 1;
X NUM
---------- ----------
1000000 1
999999 2
999998 3
999997 4
999996 5
999995 6
999994 7
999993 8
999992 9
999991 10
10 rows selected
Executed in 1.844 seconds
SQL> --B方法
SQL> SELECT *
2 FROM (SELECT x, rownum num FROM (SELECT x FROM test_table ORDER BY x DESC))
3 WHERE num BETWEEN 1 AND 10;
X NUM
---------- ----------
1000000 1
999999 2
999998 3
999997 4
999996 5
999995 6
999994 7
999993 8
999992 9
999991 10
10 rows selected
Executed in 6.906 seconds
SQL> --999991至1000000行
SQL> --A方法
SQL> SELECT *
2 FROM (SELECT /*+ first_rows */
3 x, rownum num
4 FROM (SELECT x FROM test_table ORDER BY x DESC)
5 WHERE rownum <= 1000000)
6 WHERE num >= 999991;
X NUM
---------- ----------
10 999991
9 999992
8 999993
7 999994
6 999995
5 999996
4 999997
3 999998
2 999999
1 1000000
10 rows selected
Executed in 6.703 seconds
SQL> --B方法
SQL> SELECT *
2 FROM (SELECT x, rownum num FROM (SELECT x FROM test_table ORDER BY x DESC))
3 WHERE num BETWEEN 999991 AND 1000000;
X NUM
---------- ----------
10 999991
9 999992
8 999993
7 999994
6 999995
5 999996
4 999997
3 999998
2 999999
1 1000000
10 rows selected
Executed in 6.469 seconds
SQL> DROP TABLE test_table;
Table dropped
Executed in 0.125 seconds
SQL> --我们可以看到，A方法优于B方法，
SQL> --特别是当分页查询的页数靠前的时候，速度差别很明显，
SQL> --只是分页在最后几页的时候，2种方法消耗的时间才差不多。