Posted by weilm on 2012-08-07 03:37 下午
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oracle中用comment on命令给表或字段加以说明,语法如下: COMMENT ON { TABLE [ schema. ] { table | view } | COLUMN [ schema. ] { table. | view. | materialized_view. } column | OPERATOR [ schema. ] operator | INDEXTYPE [ schema. ] indextype | MATERIALIZED VIEW materialized_view } IS 'text' ; 用法如下: 1.对表的说明 comment on table table_name is 'comments_on_tab_information'; 2.对表中列的说明 comment on column table.column_name is 'comments_on_col_information'; 3.查看表的说明 SQL> select * from user_tab_comments where TABLE_NAME='EMPLOYEES'; TABLE_NAME TABLE_TYPE COMMENTS ------------------------------ ----------- ---------- EMPLOYEES TABLE 员工表 SQL> select * from user_tab_comments where comments is not null; TABLE_NAME TABLE_TYPE COMMENTS ------------------------------ ----------- -------------------------- EMPLOYEES TABLE 员工表 4.查看表中列的说明 SQL> select * from user_col_comments where TABLE_NAME='EMPLOYEES'; TABLE_NAME COLUMN_NAME COMMENTS ------------------------------ ------------------------------ ------------ EMPLOYEES EMPLOYEE_ID EMPLOYEES MANAGER_ID EMPLOYEES FIRST_NAME EMPLOYEES LAST_NAME EMPLOYEES TITLE EMPLOYEES SALARY 员工薪水 SQL> select * from user_col_comments where comments is not null; TABLE_NAME COLUMN_NAME COMMENTS ------------------------------ ------------------------------ ------------- EMPLOYEES SALARY 员工薪水 5.我们也可以从下面这些视图中查看表级和列级说明: ALL_COL_COMMENTS USER_COL_COMMENTS ALL_TAB_COMMENTS USER_TAB_COMMENTS 6.删除表级说明,也就是将其置为空 SQL> comment on table employees is ''; Comment added SQL> select * from user_tab_comments where TABLE_NAME='EMPLOYEES'; TABLE_NAME TABLE_TYPE COMMENTS ------------------------------ ----------- ------------- EMPLOYEES TABLE 7.删除列级说明,也是将其置为空 SQL> comment on column employees.salary is ''; Comment added SQL> select * from user_col_comments where TABLE_NAME='EMPLOYEES'; TABLE_NAME COLUMN_NAME COMMENTS ------------------------------ ------------------------------ ------------- EMPLOYEES EMPLOYEE_ID EMPLOYEES MANAGER_ID EMPLOYEES FIRST_NAME EMPLOYEES LAST_NAME EMPLOYEES TITLE EMPLOYEES SALARY
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