Whether the where condition has different order and performance problems

The where condition order is different, and the performance is also different. When I saw SQL statement optimization in the book yesterday, the where condition order is different, and the performance is different. Is this recommended for Oracle11G ??? Method 1 is better than method 2 ???????? Method 1: select. * from students s, class cwhere s. id = c. id s. id = 'xxxxxxxx' Method 2: select. * from students s, class cwhere s. id = 'xxxxxxxx' s. id = c. the test results in id 10g prove to be the same. Microsoft Windows [version 5.2.3790] (C) Copyright: 1985-2003 Microsoft Corp. c: \ Documents ents and Settings \ Administrator> sqlplus/as sysdbaSQL * Plus: Release 10.2.0.1.0-Production on Saturday May 11 17:48:55 2013 Copyright (c) 1982,200 5, Oracle. all rights reserved. connect to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0-ProductionWith the Partitioning, OLAP and Data Mining optionsSQL> alter system flush shar Ed_pool; the system has been changed. SQL> alter system flush buffer_cache; the system has changed. SQL> set autotrace on; SQL> select * 2 from COUNTRIES c, 3 REGIONS r 4 where c. REGION_ID = r. REGION_ID and c. REGION_ID = '4'; REGIONS r * 3rd row error: ORA-00942: Table or view does not exist SQL> select * 2 from hr. COUNTRIES c, 3 hr. REGIONS r 4 where c. REGION_ID = r. REGION_ID and c. REGION_ID = '4'; CO COUNTRY_NAME REGION_ID -- ---------------------------------------- ---------- REGION_NAME-------------------------E G Egypt 4 4 4 Middle East and region Israel 4 4 Middle East and region Kuwait 4 4 Middle East and Africa CO COUNTRY_NAME REGION_ID -- region ---------- REGION_NAME-------------------------NG nieria 4 4 Middle East and region Zambia 4 4 Middle East and AfricaZW Zimbabwe 4 4 Middle East and Africa have selected 6 rows. Execution Plan -------------------------------------------------------- Plan hash value: 4030513296 Bytes | Id | Operation | Name | Rows | Bytes | Cost (% CPU) | Time | minute | 0 | select statement | 6 | 168 | 2 (0) | 00:00:01 | 1 | Nested loops | 6 | 168 | 2 (0) | 00:00:01 | 2 | table access by index rowid | REGIONS | 1 | 14 | 1 (0) | 00:00:01 | * 3 | index unique scan | REG_ID_PK | 1 | 0 (0) | 00:00:01 | * 4 | index full scan | COUNTRY_C_ID_PK | 6 | 84 | 1 (0) | 00:00:01 | identified Predicate Information (identified by operation id ):----- -------------------------------------------- 3-access ("R ". "REGION_ID" = 4) 4-filter ("C ". "REGION_ID" = 4) statistics 628 recursive cballs 0 db block gets 127 consistent gets 20 physical reads 0 redo size 825 bytes sent via SQL * Net to client 385 bytes received via SQL * Net from client 2 SQL * net roundtrips to/from client 13 sorts (memory) 0 sorts (d Isk) 6 rows processedSQL ############# SQL> alter system flush shared_pool; the system has been changed. SQL> alter system flush buffer_cache; the system has changed. Select * from hr. COUNTRIES c, hr. REGIONS r where c. REGION_ID = '4' 6 and c. REGION_ID = r. REGION_ID; CO COUNTRY_NAME REGION_ID -- region ---------- REGION_NAME-------------------------EG Egypt 4 4 Middle East and region Israel 4 4 Middle East and region Kuwait 4 4 Middle East and Africa CO COUNTRY_NAME REGION_ID region -- Region --------------------------- --------------- ---------- REGION_NAME-------------------------NG nieria 4 4 Middle East and AfricaZM Zambia 4 4 Middle East and AfricaZW Zimbabwe 4 4 Middle East and Africa has selected 6 rows. Execution Plan -------------------------------------------------------- Plan hash value: 4030513296 Bytes | Id | Operation | Name | Rows | Bytes | Cost (% CPU) | Time | minute | 0 | select statement | 6 | 168 | 2 (0) | 00:00:01 | 1 | nested loops | 6 | 168 | 2 (0) | 00:00:01 | 2 | table access by index rowid | REGIONS | 1 | 14 | 1 (0) | 00:00:01 | * 3 | index unique scan | REG_ID_PK | 1 | 0 (0) | 00:00:01 | * 4 | index full scan | COUNTRY_C_ID_PK | 6 | 84 | 1 (0) | 00:00:01 | identified Predicate Information (identified by operation id ): ------------------------------------------------- 3-access ("R ". "REGION_ID" = 4) 4-filter ("C ". "REGION_ID" = 4) statistics 656 recursive cballs 0 db block gets 131 consistent gets 22 physical reads 0 redo size 825 bytes sent via SQL * Net to client 385 bytes received via SQL * Net from client 2 SQL * net roundtrips to/from client 13 sorts (memory) 0 sorts (disk) 6 rows processedSQL>