Hi everybody,

at the moemnt I am writing a little app that uses the libpq client
library.

The function PQfnumber returns the column number associated with a
given column name.

Here is the spec of the function:

<snip------------------>
PQfnumber Returns the column number associated with the given column
name.
int PQfnumber(const PGresult *res, const char *column_name);

-1 is returned if the given name does not match any column. The given
name is treated like an identifier in an SQL command,
that is, it is downcased unless double-quoted.
For example, given a query result generated from the SQL command

select 1 as FOO, 2 as "BAR";

we would have the results:

PQfnumber(res, "FOO") 0
PQfnumber(res, "foo") 0
PQfnumber(res, "BAR") -1
PQfnumber(res, "\"BAR\"") 1
<snap------------------->

What happens if the statement looks like:

select 1 as FOO, 2 as FOO; (the database has no probs with that)

What result will PQfnumber return ????

PQfnumber(res, "FOO") 0 or 1 ???

Thx for all help!

Ralf Hasemann


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Ralf Hasemann <rhasemann (AT) mac (DOT) com> writes:
When in doubt, look in the source code ...

/*
* PQfnumber: find column number given column name
*
* The column name is parsed as if it were in a SQL statement, including
* case-folding and double-quote processing. But note a possible gotcha:
* downcasing in the frontend might follow different locale rules than
* downcasing in the backend...
*
* Returns -1 if no match. In the present backend it is also possible
* to have multiple matches, in which case the first one is found.
*/


regards, tom lane

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