Re: psql \set variables in crosstab queries?

On 3/4/23 19:22, Tom Lane wrote:
> Ron <ronljohnsonjr(at)gmail(dot)com> writes:
>> According to
>> https://www.postgresql.org/docs/12/app-psql.html#APP-PSQL-VARIABLES and
>> experience, variables don't interpolate inside of string literals:
>> "
>> Variable interpolation will not be performed within quoted SQL literals and
>> identifiers. Therefore, a construction such as ':foo' doesn't work to
>> produce a quoted literal from a variable's value.
>> "
>> But crosstab takes text strings as parameters.  How then do you use \set
>> variables in crosstab queries?
> If you read a little further, you'll find out the syntax for converting
> the value of a psql variable to a SQL string literal:
>
> regression=# \set foo BAR
> regression=# select ':foo';
> ?column?
> ----------
> :foo
> (1 row)
>
> regression=# select :'foo';
> ?column?
> ----------
> BAR
> (1 row)
>
> What the server got in the last case was "select 'BAR';".

postgres=# \set foo BAR
postgres=# select :'foo';
 ?column?
----------
 BAR
(1 row)

postgres=# select $$ :foo $$;
 ?column?
----------
  :foo
(1 row)

postgres=# select $$ :'foo' $$;
 ?column?
----------
  :'foo'
(1 row)

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