Re: ERROR: missing FROM-clause entry for table "new"

On Sep 13, 2012, at 20:40, James Sharrett <jsharrett(at)tidemark(dot)net> wrote:

> I'm trying to define a trigger function that looks for changes in table A (table the trigger for the function is on) and write a delta record into table B. So if a record has a value of 100 in table A, and it is updated to 50, the function should write –50 in table B. I can get the trigger to work with static SQL statements but for the actual code, I need to use dynamic SQL because I need to alter the insert statement to B depending on what column in table A is altered. I can get the correct SQL generated but when I execute the string inside the trigger function I get an error because it doesn't seem to be able to see the NEW table when it's run with EXECUTE.
>
> So, this works in the trigger function:
>
> Insert into A (col1,col2,…colN)
> Select new.col1,new.co2…new.colN)
>
> This doesn't:
>
> sql := 'Insert into A (col1,col2,…colN) ';
> sql := sql || 'Select new.col1,new.co2…new.colN)';
> Execute sql;
>
> ERROR: missing FROM-clause entry for table "new"
>
> There is nothing wrong with the resulting code from sql because if I output the string and put it in as static SQL in my trigger it works.
>
> How do I build the string within the trigger and execute it with a reference to NEW?
>
> Thanks in advance for the help,
> James
>

Please read all of:

http://www.postgresql.org/docs/9.2/interactive/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN

But especially 39.5.4

You want to make use of format and/or USING to pass in the values to a parameterized dynamic statement.

Note I linked to 9.2 but any recent version should have the behavior, if different section numbers.

In short the whole "NEW.name" is a variable and you need to build the statement the same way you would with any user-defined variable.

David J.