这篇文章主要介绍“Oracle12.2怎么修改表的列名”，在日常操作中，相信很多人在Oracle12.2怎么修改表的列名问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”Oracle12.2怎么修改表的列名”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
下面的例子将演示联机重定义使用VPD策略的表，并修改表中的一个列名，原始表jy.orders的创建语句如下:
SQL> create table jy.orders(
2 order_id number(12) primary key,
3 order_date timestamp with local time zone constraint order_date_nn not null,
4 order_mode varchar2(8),
5 customer_id number(6) constraint order_customer_id_nn not null,
6 order_status number(2),
7 order_total number(8,2),
8 sales_rep_id number(6),
9 promotion_id number(6),
10 constraint order_mode_lov
11 check (order_mode in ('direct','online')),
12 constraint order_total_min
13 check (order_total >= 0));
Table created.创建下面的jy.auth_orders函数来创建VPD策略
SQL> create or replace function jy.auth_orders( 2 schema_var in varchar2, 3 table_var in varchar2 4 ) 5 return varchar2 6 as 7 return_val varchar2 (400); 8 unm varchar2(30); 9 begin 10 select user into unm from dual; 11 if (unm = 'jy') then 12 return_val := null; 13 else 14 return_val := 'sales_rep_id = 159'; 15 end if; 16 return return_val; 17 end auth_orders; 18 / Function created.
下面执行dbms_rls.add_policy过程来使用jy.auth_orders函数来给原始表jy.orders指定VPD策略:
SQL> begin 2 dbms_rls.add_policy( 3 object_schema => 'jy', 4 object_name => 'orders', 5 policy_name => 'orders_policy', 6 function_schema => 'jy', 7 policy_function => 'auth_orders'); 8 end; 9 / PL/SQL procedure successfully completed.
在这个例子中，被重定义后表中的sales_rep_id列被修改为sale_pid。当在执行重定义过程如可修改一个或多个列或列的数据类型，那么在start_refef_table过程中对于copy_vpd_opt参数必须指定dbms_redefinition.cons_vpd_manual。
1.用要执行联机重定义操作的用户登录数据库
SQL> conn jy/jy@jypdb Connected.
2.验证原始表是否可以执行联机重定义
SQL> begin 2 dbms_redefinition.can_redef_table( 3 uname => 'jy', 4 tname => 'orders', 5 options_flag => DBMS_REDEFINITION.CONS_USE_PK); 6 end; 7 / PL/SQL procedure successfully completed.
3.创建中间表
SQL> create table jy.int_orders( 2 order_id number(12), 3 order_date timestamp with local time zone, 4 order_mode varchar2(8), 5 customer_id number(6), 6 order_status number(2), 7 order_total number(8,2), 8 sales_pid number(6), 9 promotion_id number(6)); Table created.
注意，在中间表中sales_rep_id列被修改为sales_pid。
4.开始联机重定义操作
SQL> begin 2 dbms_redefinition.start_redef_table ( 3 uname => 'jy', 4 orig_table => 'orders', 5 int_table => 'int_orders', 6 col_mapping => 'order_id order_id, order_date order_date, order_mode 7 order_mode, customer_id customer_id, order_status 8 order_status, order_total order_total, sales_rep_id 9 sales_pid, promotion_id promotion_id', 10 options_flag => dbms_redefinition.cons_use_pk, 11 orderby_cols => null, 12 part_name => null, 13 copy_vpd_opt => dbms_redefinition.cons_vpd_manual); 14 end; 15 / PL/SQL procedure successfully completed.
因为原始表与中间表存在不同的列名，那么copy_vpd_opt参数必须设置为dbms_redefinition.cons_vpd_manual。
5.对中间表创建VPD策略
5.1创建一个名为jy.auth_orders_sales_pid的函数来创建VPD策略，这里使用sales_pid列来代替sales_rep_id列。
SQL> create or replace function jy.auth_orders_sales_pid( 2 schema_var in varchar2, 3 table_var in varchar2 4 ) 5 return varchar2 6 as 7 return_val varchar2 (400); 8 unm varchar2(30); 9 begin 10 select user into unm from dual; 11 if (unm = 'jy') then 12 return_val := null; 13 else 14 return_val := 'sales_pid = 159'; 15 end if; 16 return return_val; 17 end auth_orders_sales_pid; 18 / Function created.
5.2执行dbms_rls.add_policy过程来使用jy.auth_orders_sales_pid函数来为中间表增加VPD策略
SQL> begin 2 dbms_rls.add_policy ( 3 object_schema => 'jy', 4 object_name => 'int_orders', 5 policy_name => 'orders_policy', 6 function_schema => 'jy', 7 policy_function => 'auth_orders_sales_pid'); 8 end; 9 / PL/SQL procedure successfully completed.
6.复制依赖对象
SQL> declare 2 num_errors pls_integer; 3 begin 4 dbms_redefinition.copy_table_dependents( 5 uname => 'jy', 6 orig_table => 'orders', 7 int_table => 'int_orders', 8 copy_indexes => dbms_redefinition.cons_orig_params, 9 copy_triggers => true, 10 copy_constraints => true, 11 copy_privileges => true, 12 ignore_errors => true, 13 num_errors => num_errors); 14 end; 15 / PL/SQL procedure successfully completed.
注意在这里ignore_errors参数被设置为true。原因是因为原始表对于列sales_rep_id存在索引与约束，并且在中间表中列被修改为sales_pid。
7.查询dba_redefinition_errors视图来检查是否存在错误
SQL> set long 8000 SQL> set pages 8000 SQL> column object_name heading 'object name' format a20 SQL> column base_table_name heading 'base table name' format a10 SQL> column ddl_txt heading 'ddl that caused error' format a40 SQL> select object_name, base_table_name, ddl_txt from dba_redefinition_errors; no rows selected
8.可选操作同中间表
SQL> begin 2 dbms_redefinition.sync_interim_table( 3 uname => 'jy', 4 orig_table => 'orders', 5 int_table => 'int_orders'); 6 end; 7 / PL/SQL procedure successfully completed.
9.完成联机重定义操作
SQL> begin 2 dbms_redefinition.finish_redef_table( 3 uname => 'jy', 4 orig_table => 'orders', 5 int_table => 'int_orders'); 6 end; 7 / PL/SQL procedure successfully completed. SQL> desc jy.orders Name Type Nullable Default Comments ------------ --------------------------------- -------- ------- -------- ORDER_ID NUMBER(12) ORDER_DATE TIMESTAMP(6) WITH LOCAL TIME ZONE ORDER_MODE VARCHAR2(8) Y CUSTOMER_ID NUMBER(6) ORDER_STATUS NUMBER(2) Y ORDER_TOTAL NUMBER(8,2) Y SALES_PID NUMBER(6) Y PROMOTION_ID NUMBER(6) Y
10.等待任何查询中间表的语句执行完成后将其删除
SQL> drop table jy.int_orders; Table dropped
到此重定义操作就完成了。
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