Oracle的表如何连接

这篇文章主要介绍Oracle的表如何连接，文中介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们一定要看完！Oracle表连接方法有四种：
● 排序合并连接（Sort Merge Join）
● 嵌套循环连接（Nested Loops Join）
● 哈希连接（Hash Join）
● 笛卡尔积（Cartesian Product）如果where条件有exists、in或=any操作符+子查询，则Oracle会将其处理为半连接，执行计划中对应的关键字为SEMI。SQL> select department_id,department_name from departments d where exists (select 1 from employees e where d.department_id = e.department_id and e.salary > 2500);11 rows selected.
Execution Plan
———————————————————-
Plan hash value: 2188966913———————-免费主机域名———————————————————————-
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
———————免费主机域名———————————————————————–
| 0 | SELECT STATEMENT | | 10 | 230 | 6 (17)| 00:00:01 |
| 1 | MERGE JOIN SEMI | | 10 | 230 | 6 (17)| 00:00:01 |
| 2 | TABLE ACCESS BY INDEX ROWID| DEPARTMENTS | 27 | 432 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | DEPT_ID_PK | 27 | | 1 (0)| 00:00:01 |
|* 4 | SORT UNIQUE | | 105 | 735 | 4 (25)| 00:00:01 |
|* 5 | TABLE ACCESS FULL | EMPLOYEES | 105 | 735 | 3 (0)| 00:00:01 |
——————————————————————————————–SQL> select department_id,department_name from departments d where department_id in (select department_id from employees e where d.department_id = e.department_id and e.salary > 2500);11 rows selected.
Execution Plan
———————————————————-
Plan hash value: 2188966913——————————————————————————————–
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
——————————————————————————————–
| 0 | SELECT STATEMENT | | 10 | 230 | 6 (17)| 00:00:01 |
| 1 | MERGE JOIN SEMI | | 10 | 230 | 6 (17)| 00:00:01 |
| 2 | TABLE ACCESS BY INDEX ROWID| DEPARTMENTS | 27 | 432 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | DEPT_ID_PK | 27 | | 1 (0)| 00:00:01 |
|* 4 | SORT UNIQUE | | 105 | 735 | 4 (25)| 00:00:01 |
|* 5 | TABLE ACCESS FULL | EMPLOYEES | 105 | 735 | 3 (0)| 00:00:01 |
——————————————————————————————–SQL> select department_id,department_name from departments d where department_id=any(select department_id from employees e where d.department_id = e.department_id and e.salary > 2500);11 rows selected.
Execution Plan
———————————————————-
Plan hash value: 2188966913——————————————————————————————–
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
——————————————————————————————–
| 0 | SELECT STATEMENT | | 10 | 230 | 6 (17)| 00:00:01 |
| 1 | MERGE JOIN SEMI | | 10 | 230 | 6 (17)| 00:00:01 |
| 2 | TABLE ACCESS BY INDEX ROWID| DEPARTMENTS | 27 | 432 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | DEPT_ID_PK | 27 | | 1 (0)| 00:00:01 |
|* 4 | SORT UNIQUE | | 105 | 735 | 4 (25)| 00:00:01 |
|* 5 | TABLE ACCESS FULL | EMPLOYEES | 105 | 735 | 3 (0)| 00:00:01 |
——————————————————————————————–以上是“Oracle的表如何连接”这篇文章的所有内容，感谢各位的阅读！希望分享的内容对大家有帮助，更多相关知识，欢迎关注云技术行业资讯频道！

相关推荐: 怎么处理ORACLE悬疑分布式事务问题

这篇文章主要讲解了“怎么处理ORACLE悬疑分布式事务问题”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“怎么处理ORACLE悬疑分布式事务问题”吧！当需要在多个Oracle数据库之间进行数据一致性操作时，就会用…