how to for loop with distinct values?

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I am banging my head over this. I want to select distinct values from a
varchar column and iterate through the values.
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*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:

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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. **
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