I have two tables with the same structure, A and B. A certain application is written so that it always writes the same data to both tables.

After a discussion with a colleague about the potential to save drive space, I'm wondering if mysql or postgresql has the ability to create on table as an "alias", or "symlink", of another.

I want the behaviour to be very similar to that of a soft file symlink; where reading from either the symlink itself or it's target will yield the same output, and writing to either will update the target.

  • 2
    Have you considered a view of the table?
    – user1240
    May 25, 2012 at 23:09
  • In SQL Server you could just use a view.
    – JNK
    May 25, 2012 at 23:10
  • 1
    Which RDBMS? You've tagged MySQL and Postgres. Views will work in most RDBMSes. Oracle has synonyms, which are the same as Unix symbolic links
    – Philᵀᴹ
    May 25, 2012 at 23:11
  • MySQL and Postgres, yes. I mention them specifically in the text as well. I thought Views was somehow not quite what I was looking for, but perhaps it will be just fine. Thanks a lot. Post some answers :)
    – user50849
    May 25, 2012 at 23:15
  • 1
    and why do you need two tables?
    – miracle173
    May 26, 2012 at 2:32

2 Answers 2


As far as I know, a new Postgresql lets you have INSTEAD OF triggers on views. So having one table, one view as SELECT * FROM table1, and INSTEAD OF trigger for insert, update, delete should work for you. This approach is not gonna work in Mysql though


It is possible in MySQL (using MyISAM storage engine only) to create a table from scratch using symlinks. It is posssible in Linux and Windows (using hardlinks) :

Here are my past posts on this subject

However, what you are proposing would have to be done outside of MySQL in Linux.

For this example

  • /var/lib/mysql is datadir
  • Create table1 as MyISAM table in database mydb
  • Create table2 as pure symlinks to table1

STEP 01) Create table1

CREATE TABLE mydb.table1
    id int not null auto_increment,
    mydata varchar(255) not null,
    primary key (id)

STEP 02) Create three symlinks to mimic TableB

cd /var/lib/mysql/mydb
ln -s table1.frm table2.frm
ln -s table1.MYD table2.MYD
ln -s table1.MYI table2.MYI

STEP 03) Try inserting into table1 and reading from table2. Then try the reverse.

INSERT INTO table1 (mydata) VALUES ('rolando'),('edwards');
SELECT * FROM table2;
INSERT INTO table2 (mydata) VALUES ('abraham'),('lincoln');
SELECT * FROM table1;

If everything behaves normal, then this is how you can do this.


  1. There is only one table, table1
  2. If you do any DDL
    • Perform the DDL on table1
    • You must recreate the table2 symlinks after DDL against table1

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