Re: how to for loop with distinct values?

On Mon, May 21, 2012 at 3:39 PM, J.V. <jvsrvcs(at)gmail(dot)com> wrote:
>
> I am banging my head over this. I want to select distinct values from a
> varchar column and iterate through the values.
>
> I want to select the distinct values from this column and loop through
them
> (using as a variable) in a raise notice statement and also in an update
> statement.
>
> I have not been able to do this trying dozens of different approaches. I
> could not find an example even after searching google.
>
> So for example, suppose table: mytable has a column "value" that is
defined
> as a varchar:
>
>
> for tmp_var in select distinct(value) from mytable where
> value2='literal'
> loop
> raise notice 'I want to print a message here - the tmp_var is ['
||
> tmp_var || ']'; <== error on this line
> update table set somecolumn = ''' || tmp_var || '''
> end loop;
>
> I want to use each distinct value in a "raise notice" line and an update
> statement.
>
> tmp_var has to be in ' ' ticks or will not work. it is failing on the
> first FOR statement stating: "invalid input syntax for integer:
> "some_distinct_value".
>
> How do I select varchar distinct values and iterate using variables in a
> raise notice statement and inside another update statement?
>
> this seems simple to do , but have not found a way.

Well it looks like you have a couple of problems here. First, when you
'raise notice', generally you do it like this:
raise notice 'value of var is %', var;

And not do string concatenation. As for the update statement, you should
be quoting tmp_var. At most you should be casting (tmp_var::int) and then
be diagnosing why you have non integer data in a value you are trying to
put into a integer column (which is the point of the insert). So, you are
very close -- it all comes down to how you are handling the NOTICE i think.
A quick review of the examples here:
http://www.postgresql.org/docs/9.2/static/plpgsql-errors-and-messages.html
might
be helpful.

merlin