On 01/27/2011 09:52 AM, Santosh Bhujbal (sabhujba) wrote:
CREATE OR REPLACE FUNCTION ColumnAlreadyExists(name, name) RETURNS
INTEGER AS E'
DECLARE columnCount INTEGER;
BEGIN
SELECT COUNT (pg_attribute.attname) into columnCount FROM
pg_attribute,pg_class, pg_type WHERE
((pg_attribute.attrelid=pg_class.oid) AND
(pg_attribute.atttypid=pg_type.oid) AND (pg_class.relname = $1) AND
(pg_attribute.attname = $2));
IF columnCount = 0 THEN
RETURN 0;
END IF;
RETURN 1;
END;
' LANGUAGE 'plpgsql';
DROP FUNCTION checkColumn(name,name,name);
CREATE OR REPLACE FUNCTION checkColumn(name, name, name) RETURNS name
AS E'
DECLARE isColumnExist INTEGER;
BEGIN
SELECT ColumnAlreadyExists ($1,$2) into isColumnExist;
IF isColumnExist = 0 THEN
RETURN name($3);
ELSE
RETURN name($2);
END IF;
END;
' LANGUAGE 'plpgsql';
Function checkColumn should return proper column name (second
parameter) if column exist and third parameter if column not exist.
NOW when I try to execute following command it returns improper result.
I expect proper column values as a output of query.
SELECT(checkColumn('tbl','c2','0'))::name FROM tbl;
mydb=# SELECT (checkColumn('tbl','c2','0'))::name FROM tbl;
checkcolumn
-------------
c2
c2
c2
c2
c2
c2
c2
c2
(8 rows)
mydb=#
Above query should return actual values present for c2 column in tbl.
But it's not working as desired.
Please help me in this.
Thanks in advance,
Santosh.
the name datatype won't cast it into a selectable column.
Forgetting about your function, if you try select 'c2'::name from tbl it
will also return c2 as a name datatype.
What you want to do is a dynamic query where you use execute or for row
in execute in a plpgsql function.
Also to see if the column exists, I would recommend using
information_schema.columns
