Oracle Snippets

By Andres Jaimes

This post will be updated with snippets for Oracle. I hope you find it useful.


1. Change the default date format

Most useful snippet of the year! 😉

select sysdate from dual;

2. Escape single quotes and ampersands on strings

Single quotes:

select 'D''Angelo''s' from dual;



3. Adjust page width and size

set pagesize 1000
set linesize 100

4. Truncate a table

Be careful: You cannot roll back a TRUNCATE TABLE statement.

truncate table mytable;

5. Send all output from sqlplus to an external log file

spool file.log
-- some commands here...
spool off

6. Load and execute in sqlplus a script from an external file


7. Print text – like a comment

PROMPT text to print;

8. Check if a table exists

select count(*) into v from all_tables where table_name='YOUR_TABLE';



if myCount = 0 then
    insert into tableName values(1, 'a');
    delete from tableName where id = 1;
    insert into tableName values(1, 'b');
end if;



You can declare as many vars as you need in the declare section.

    myCount integer;
    select count(1) into myCount from aTable where aField = 1;
    if myCount = 0 then
        insert into tableName values(1, 'a');
        delete from tableName where id = 1;
        insert into tableName values(1, 'b');
    end if;



create database link <my-connection-alias> connect to <my-user> identified by <my-password> using '<server:port/sid>';

Drop a link to a remote server

drop database link


Execute a “select” on a remote server

select count(*) from <my-remote-table>@<my-connection-alias>;


Create a local copy of a remote table

create table <my-local-table> as select * from <my-remote-table>@<my-connection-alias>;


Append data to a local table created from a remote table

insert into <my-local-table> * from <my-remote-table>@<my-connection-alias> where...;


select * from ALL_DB_LINKS;

You can choose from here:

  • DBA_DB_LINKS: All db links in the database
  • ALL_DB_LINKS: All db links the current user has access to
  • USER_DB_LINKS: All db links owned by the current user


SQL Developer

Autoformat your SQL code:

ctrl + F7

Autoformat SQL code for other languages:

ctrl + shift + F7

Add a TNS file:

  • Go to Tools > Preferences > Database > Advanced > Tnsnames Directory


Oracle XE

Common installation directory


Size of tablespaces

Oracle XE 11g has a space limit of 11Gb for the Users tablespace (all others do not add up to this total). If your tablespace for Users says something like 99% of 300Mb, don’t worry, it will keep growing until it reaches its max limit.

SELECT /* + RULE */  df.tablespace_name "Tablespace",
  df.bytes / (1024 * 1024) "Size (MB)",
  SUM(fs.bytes) / (1024 * 1024) "Free (MB)",
  Nvl(Round(SUM(fs.bytes) * 100 / df.bytes),1) "% Free",
  Round((df.bytes - SUM(fs.bytes)) * 100 / df.bytes) "% Used"
FROM dba_free_space fs,
  (SELECT tablespace_name,SUM(bytes) bytes
   FROM dba_data_files
   GROUP BY tablespace_name) df
WHERE fs.tablespace_name (+)  = df.tablespace_name
GROUP BY df.tablespace_name,df.bytes
SELECT /* + RULE */ df.tablespace_name tspace,
  fs.bytes / (1024 * 1024),
  SUM(df.bytes_free) / (1024 * 1024),
  Nvl(Round((SUM(fs.bytes) - df.bytes_used) * 100 / fs.bytes), 1),
  Round((SUM(fs.bytes) - df.bytes_free) * 100 / fs.bytes)
FROM dba_temp_files fs,
  (SELECT tablespace_name,bytes_free,bytes_used
   FROM v$temp_space_header
   GROUP BY tablespace_name,bytes_free,bytes_used) df
WHERE fs.tablespace_name (+)  = df.tablespace_name
GROUP BY df.tablespace_name,fs.bytes,df.bytes_free,df.bytes_used