Some sql commands commonly used in oracle

/ / check the current time of the system HH24 24-hour system MI is the correct minute

Select to_char (sysdate,'yyyy-mm-dd HH24:MI:SS') from dual

/ / HH non-24 mm case-insensitive dates are considered to be months by the MM system

Select to_char (sysdate,'yyyy-mm-dd HH:MM:SS') from dual

/ / report the system date in TIMESTAMP data type format.

Select SYSTIMESTAMP from dual

/ / query the currently logged in user

Select username from user_users

Show user

/ / View table structure (field data type)

Desc user_users

/ / query the tables owned by the current user

Select table_name from user_tables

/ / forget your password to log in

Open the cmd window and enter sqlplus / as sysdba

/ / remote connection

Gb/ruiyuan@192.168.0.210/orcl

/ / create a sequence

Create sequence sequence name

Start with start sequence

The value of each increase in increment by

Sequence name .nextval (next sequence)

Sequence name .currval (current sequence)

/ / create reply temporary table data

Create global temporary table table as another table data on commit preserve rows; (you can copy the data in the original table, which is more commonly used. )

/ / add field comments (table comments)

Comment on column tmp_xian.id is' primary key'

Comment on column tmp_xian.name is' maximum user name'

COMMENT ON TABLE TABLENAME IS 'user Table'

/ / varchar2 maximum length 4000bite char (2000bite)

/ / View the first 500 rows of data

Select * from T_PUB_DOWNLOAD_DETAIL where rownum