Oracle的分頁查詢語句基本上可以按照本文給出的格式來進(jìn)行套用。
創(chuàng)新互聯(lián)是專業(yè)的三河網(wǎng)站建設(shè)公司，三河接單;提供網(wǎng)站制作、成都網(wǎng)站設(shè)計,網(wǎng)頁設(shè)計,網(wǎng)站設(shè)計,建網(wǎng)站,PHP網(wǎng)站建設(shè)等專業(yè)做網(wǎng)站服務(wù);采用PHP框架,可快速的進(jìn)行三河網(wǎng)站開發(fā)網(wǎng)頁制作和功能擴(kuò)展;專業(yè)做搜索引擎喜愛的網(wǎng)站,專業(yè)的做網(wǎng)站團(tuán)隊(duì),希望更多企業(yè)前來合作!
Oracle分頁查詢語句（一）：http://yangtingkun.itpub.net/post/468/100278
這篇文章用幾個例子來說明分頁查詢的效率。首先構(gòu)造一個比較大的表作為測試表：
SQL> CREATE TABLE T AS SELECT * FROM DBA_OBJECTS, DBA_SEQUENCES;
表已創(chuàng)建。
SQL> SELECT COUNT(*) FROM T;
COUNT(*)
----------
457992
首先比較兩種分頁方法的區(qū)別：
SQL> SET AUTOT ON
SQL> COL OBJECT_NAME FORMAT A30
SQL> EXEC DBMS_STATS.GATHER_TABLE_STATS(USER, 'T')
PL/SQL 過程已成功完成。
SQL> SELECT OBJECT_ID, OBJECT_NAME
2 FROM
3 (
4 SELECT ROWNUM RN, OBJECT_ID, OBJECT_NAME
5 FROM
6 (
7 SELECT OBJECT_ID, OBJECT_NAME FROM T
8 )
9 )
10 WHERE RN BETWEEN 11 AND 20;
OBJECT_ID OBJECT_NAME
---------- ------------------------------
5807 ALL_APPLY_PROGRESS
1769 ALL_ARGUMENTS
2085 ALL_ASSOCIATIONS
4997 ALL_AUDIT_POLICIES
4005 ALL_BASE_TABLE_MVIEWS
5753 ALL_CAPTURE
5757 ALL_CAPTURE_PARAMETERS
5761 ALL_CAPTURE_PREPARED_DATABASE
5765 ALL_CAPTURE_PREPARED_SCHEMAS
5769 ALL_CAPTURE_PREPARED_TABLES
已選擇10行。
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=864 Card=457992 Bytes=42135264)
1 0 VIEW (Cost=864 Card=457992 Bytes=42135264)
2 1 COUNT
3 2 TABLE ACCESS (FULL) OF 'T' (Cost=864 Card=457992 Bytes=9617832)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
8979 consistent gets
7422 physical reads
0 redo size
758 bytes sent via SQL*Net to client
503 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
10 rows processed
SQL> SELECT OBJECT_ID, OBJECT_NAME
2 FROM
3 (
4 SELECT ROWNUM RN, OBJECT_ID, OBJECT_NAME
5 FROM
6 (
7 SELECT OBJECT_ID, OBJECT_NAME FROM T
8 )
9 WHERE ROWNUM <= 20
10 )
11 WHERE RN >= 11;
OBJECT_ID OBJECT_NAME
---------- ------------------------------
5807 ALL_APPLY_PROGRESS
1769 ALL_ARGUMENTS
2085 ALL_ASSOCIATIONS
4997 ALL_AUDIT_POLICIES
4005 ALL_BASE_TABLE_MVIEWS
5753 ALL_CAPTURE
5757 ALL_CAPTURE_PARAMETERS
5761 ALL_CAPTURE_PREPARED_DATABASE
5765 ALL_CAPTURE_PREPARED_SCHEMAS
5769 ALL_CAPTURE_PREPARED_TABLES
已選擇10行。
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=864 Card=20 Bytes=1840)
1 0 VIEW (Cost=864 Card=20 Bytes=1840)
2 1 COUNT (STOPKEY)
3 2 TABLE ACCESS (FULL) OF 'T' (Cost=864 Card=457992 Bytes=9617832)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
5 consistent gets
0 physical reads
0 redo size
758 bytes sent via SQL*Net to client
503 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
10 rows processed
二者執(zhí)行效率相差很大，一個需要8000多邏輯讀，而另一個只需要5個邏輯讀。觀察二者的執(zhí)行計劃可以發(fā)現(xiàn)，兩個執(zhí)行計劃唯一的區(qū)別就是第二個查詢在COUNT這步使用了STOPKEY，也就是說，Oracle將ROWNUM <= 20推入到查詢內(nèi)層，當(dāng)符合查詢的條件的記錄達(dá)到STOPKEY的值，則Oracle結(jié)束查詢。
因此，可以預(yù)見，采用第二種方式，在翻頁的開始部分查詢速度很快，越到后面，效率越低，當(dāng)翻到最后一頁，效率應(yīng)該和第一種方式接近。
SQL> SELECT OBJECT_ID, OBJECT_NAME
2 FROM
3 (
4 SELECT ROWNUM RN, OBJECT_ID, OBJECT_NAME
5 FROM
6 (
7 SELECT OBJECT_ID, OBJECT_NAME FROM T
8 )
9 WHERE ROWNUM <= 457990
10 )
11 WHERE RN >= 457980;
OBJECT_ID OBJECT_NAME
---------- ------------------------------
7128 XCF_I_HANDLE_STATUS
7126 XCF_P
7127 XCF_U1
7142 XDF
7145 XDF_I_DF_KEY
7146 XDF_I_HANDLE_STATUS
7143 XDF_P
7144 XDF_U1
TEST.YANGTINGKUN
TEST4.YANGTINGKUN
YANGTK.YANGTINGKUN
已選擇11行。
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=864 Card=457990 Bytes=42135080)
1 0 VIEW (Cost=864 Card=457990 Bytes=42135080)
2 1 COUNT (STOPKEY)
3 2 TABLE ACCESS (FULL) OF 'T' (Cost=864 Card=457992 Bytes=9617832)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
8979 consistent gets
7423 physical reads
0 redo size
680 bytes sent via SQL*Net to client
503 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
11 rows processed
重慶分公司
重慶分公司
