Oracle questions, 10 questions every day (5)

41. How do I add comments to tables and columns?

SQL> comment on table is 'table annotation'; the comment has been created.

SQL> comment on column table. The column is 'column annotation'; the comment has been created.

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

42. How can I view the disk usage of each tablespace?

SQL> Col tablespace format A20

SQL> select

B. ID of the file_id file,

B. tablespace_name: name of the tablespace,

B. bytes,

(B. bytes-sum (nvl (A. bytes, 0) already in use,

Sum (nvl (A. bytes, 0) remaining space,

Sum (nvl (A. bytes, 0)/(B. bytes) * 100 percentage remaining

From dba_free_space A, dba_data_files B

Where a. file_id = B. file_id

Group by B. tablespace_name, B. file_id, B. bytes

Order by B. file_id

43. If Oracle is set to MTS or dedicated mode?

# Dispatchers = "(Protocol = TCP) (Service = sidxdb)" with MTS, annotation is the dedicated mode, and Sid is your instance name.

44. How can I know the current SCN Number of the system?

Select max (ktuxescnw * power (2, 32) + ktuxescnb) from x $ ktuxe;

45. How can I retrieve milliseconds in Oracle?

Not Supported before 9i, 9i starts to have timestamp.

9i can use select distinct imestamp from dual;

46. How do I add a carriage return to the string?

Select 'Welcome to visit' | CHR (10) | 'www. csdn. net' from dual;

47. How is Chinese sorted?

Before Oracle9i, Chinese characters were sorted by binary encoding.

The sorting by pinyin, radical, and stroke function is added to Oracle9i. Set the nls_sort Value

Schinese_radical_m is sorted by the beginning (first order) and strokes (Second Order ).

Schinese_stroke_m is sorted by strokes (first order) and heads (Second Order ).

Schinese_pinyin_m is sorted by pinyin

48. Can the object name in Oracle8i be in Chinese?

Yes

49. How to change the SQL * Plus startup option in win?

You can set SQL * Plus options in $ ORACLE_HOME/sqlplus/admin/glogin. SQL.

50. How do I modify the default date of the replicel database?

Alter session set nls_date_format = 'yyyymmddhh24miss ';

Or

You can add a line in init. ora.

Nls_date_format = 'yyyymmddhh24miss'