欧美一区二区成人精品视频,日本一区二区三区三州在线观看视频

oracle中用comment on命令給表或字段加以說(shuō)明，語(yǔ)法如下：

復(fù)制代碼代碼如下:

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.對(duì)表的說(shuō)明

復(fù)制代碼代碼如下:

comment on table table_name is 'comments_on_tab_information';

2.對(duì)表中列的說(shuō)明

復(fù)制代碼代碼如下:

comment on column table.column_name is 'comments_on_col_information';

3.查看表的說(shuō)明

復(fù)制代碼代碼如下:

SQL> select * from user_tab_comments where TABLE_NAME='EMPLOYEES';

復(fù)制代碼代碼如下:

TABLE_NAME TABLE_TYPE COMMENTS
------------------------------ ----------- ----------
EMPLOYEES TABLE 員工表

SQL> select * from user_tab_comments where comments is not null;

TABLE_NAME TABLE_TYPE COMMENTS
------------------------------ ----------- --------------------------
EMPLOYEES TABLE 員工表

4.查看表中列的說(shuō)明

復(fù)制代碼代碼如下:

SQL> select * from user_col_comments where TABLE_NAME='EMPLOYEES';

復(fù)制代碼代碼如下:

TABLE_NAME                     COLUMN_NAME                    COMMENTS
------------------------------ ------------------------------ ------------
EMPLOYEES                      EMPLOYEE_ID
EMPLOYEES                      MANAGER_ID
EMPLOYEES                      FIRST_NAME
EMPLOYEES                      LAST_NAME
EMPLOYEES                      TITLE
EMPLOYEES                      SALARY                         員工薪水

SQL> select * from user_col_comments where comments is not null;

TABLE_NAME COLUMN_NAME COMMENTS
------------------------------ ------------------------------ -------------
EMPLOYEES SALARY 員工薪水

5.我們也可以從下面這些視圖中查看表級(jí)和列級(jí)說(shuō)明：

復(fù)制代碼代碼如下:

ALL_COL_COMMENTS
USER_COL_COMMENTS
ALL_TAB_COMMENTS
USER_TAB_COMMENTS 

6.刪除表級(jí)說(shuō)明，也就是將其置為空

復(fù)制代碼代碼如下:

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.刪除列級(jí)說(shuō)明，也是將其置為空

復(fù)制代碼代碼如下:

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

您可能感興趣的文章:

Oracle數(shù)據(jù)庫(kù)執(zhí)行腳本常用命令小結(jié)
oracle創(chuàng)建表的方法和一些常用命令
oracle數(shù)據(jù)庫(kù)導(dǎo)入導(dǎo)出命令解析

標(biāo)簽：宜春孝感六安淮南海北葫蘆島泰安酒泉

巨人網(wǎng)絡(luò)通訊聲明：本文標(biāo)題《oracle comment命令用法示例分享》，本文關(guān)鍵詞 oracle,comment,命令,用法,示例,；如發(fā)現(xiàn)本文內(nèi)容存在版權(quán)問(wèn)題，煩請(qǐng)?zhí)峁┫嚓P(guān)信息告之我們，我們將及時(shí)溝通與處理。本站內(nèi)容系統(tǒng)采集于網(wǎng)絡(luò)，涉及言論、版權(quán)與本站無(wú)關(guān)。