Some SQL commands commonly used by Oracle

View system Current time HH24 24-hour MI is the right minute

Select To_char (sysdate, ' Yyyy-mm-dd HH24:MI:SS ') from dual

HH non-MM case-insensitive date mm system is considered a month

Select To_char (sysdate, ' Yyyy-mm-dd HH:MM:SS ') from dual

Reports the system date in timestamp data type format.

Select Systimestamp from dual;

Querying the currently logged on user

Select username from user_users

Show user

View table structure (field data type)

Desc user_users

Querying tables owned by the current user

Select table_name from User_tables

Forgot Password Login

Open the cmd window and enter Sqlplus/as SYSDBA

Remote connection

Gb/[email PROTECTED]/ORCL

Create a sequence

Create sequence sequence name

Start with start sequence

Increment by value per increment

Sequence name. Nextval (Next sequence)

Sequence name. Currval (current sequence)

Create a reply temp table data

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

Add a field comment (Table note)

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<500

COUNT (*) and COUNT (1) Efficiency results are the same as count (name) statistic Name column is not empty record

Select COUNT (*) from table; COUNT (1)

Date datetime (accurate to seconds) timestamp (accurate to fractional seconds)

Union Table link (filter duplicate records) union ALL (simple 2 tables result merge) union ALL high efficiency

LTRIM (String): Remove the space to the left of the string. 　　RTRIM (String): Removes the space to the right of the string. 　　TRIM (String): Removes the spaces at the beginning and end of the string. ALLTRIM (String): Remove the space between the left and right sides of the string.

Some SQL commands commonly used by Oracle