Question

Possible Duplicate:
Update row with data from another row in the same table

I have created table as

create table myTable (id INT, myData varchar(20));

And I have values as

insert into myTable VALUES 
(1, 'Value 1'),
(2, 'Value 2'),
(3, 'Value 3');

Now I insert row as

insert into myTable (id) values (4);

Now I want to insert data for id 4. Value for id 4 is same as id 3. SO I believe I need to use UPDATE statement.

I tried with below, however it won’t work.

 update myTable SET myData=(select myData FROM myTable WHERE id=3) WHERE id=4;

Please let me know what need to be done.

Demo at sqlfiddle

NOTE

Actually I have myData type as MEDIUMBLOB, however for demo purpose I used varchar.

Answer 1

In MySQL you can’t update the same table your are selecting from. That leads to the error

You can’t specify target table ‘myTable’ for update in FROM clause

But you can trick MySQL by creating a temp table

update myTable
SET myData=(select * from (select myData FROM myTable WHERE id=3) x)
WHERE id=4;