This function works:
CREATE OR REPLACE FUNCTION public.a()
RETURNS TABLE(a text)
LANGUAGE plpgsql
AS $function$
BEGIN
return query execute
'select a from ztable';
END;
$function$;
But when I try to add some text to the column name:
CREATE OR REPLACE FUNCTION public.a(prefix text)
RETURNS TABLE(a text)
LANGUAGE plpgsql
AS $function$
BEGIN
return query execute
'select a as $1_a from ztable' using prefix;
END;
$function$;
This just fails as a syntax error on $1.
Or:
CREATE OR REPLACE FUNCTION public.a(prefix text)
RETURNS TABLE(a text)
LANGUAGE plpgsql
AS $function$
BEGIN
return query execute
'select a as '||prefix||'_a from ztable';
END;
$function$;
select * from a('some prefix') doesn't work.
Is there some other syntax that does the job?
That's simply not possible. SQL does not allow dynamic column names.
You must assign a column alias with the call. Like:
SELECT a AS prefix_a FROM public.a();
Or in a column definition list directly attached to the function:
SELECT * FROM public.a() AS f(prefix_a);
Or, while dealing with a single output column, even just:
SELECT * FROM public.a() AS prefix_a;
See:
RETURNING rows using unnest()?
Related
How to assign results of REPLACE() built-in Postgres function to another variable?
I am trying something like this, but it does not work:
CREATE FUNCTION uri2text(uri text) RETURNS text AS $$
SET temp_text = SELECT REPLACE(uri , '%20', ' ');
RETURN temp_text;
$$ LANGUAGE SQL;
You can't have variables in SQL (which is the language that language sql selects for the function). To use variables, you need PL/pgSQL, and as documented in the manual assignment is done using := (or =) in PL/pgSQL. And you need to declare a variable before you can use it.
You also don't need a SELECT statement to call a function.
So if you do want to use PL/pgSQL, the function needs to look like this:
CREATE FUNCTION uri2text(uri text)
RETURNS text
AS $$
declare
temp_text text;
begin
temp_text := REPLACE(uri , '%20', ' ');
RETURN temp_text;
end;
$$ LANGUAGE plpgsql;
However you wouldn't even need a variable:
CREATE FUNCTION uri2text(uri text)
RETURNS text
AS $$
begin
RETURN REPLACE(uri , '%20', ' ');
end;
$$ LANGUAGE plpgsql;
And you don't even need PL/pgSQL for this:
CREATE FUNCTION uri2text(uri text)
RETURNS text
AS $$
SELECT REPLACE(uri , '%20', ' ');
$$ LANGUAGE sql;
Note that in case of the SQL function, you do need the SELECT because in SQL there is no return or assignment.
How do i create a Procedure that returns a set of rows from a table?
or is it even possible to return a tabular result set with procedure.
I tried adding returns setof students like you do in a function and table(id int) but it doesn't work.
SAMPLE CODE:
CREATE OR REPLACE PROCEDURE getStudents()
LANGUAGE plpgsql
AS $$
BEGIN
SELECT * FROM STUDENTS
COMMIT;
RETURN;
END;
$$;
I can call it but it says query has no destination for result data
Procedures aren't meant to return data, that's what functions are for.
You can use a plain SQL function for this, no need for PL/pgSQL:
CREATE OR REPLACE funct get_students()
returns setof student
LANGUAGE sqö
AS $$
select *
from students;
$$;
Then use it like a table:
select *
from get_students();
There is also no need for a commit.
Try to use function instead of procedure. I usually use this.
You need to create a ctype for fetching the data.
Put whatever columns you have to fetch from STUDENTS table.
Syntax is as follows:
CREATE TYPE students_data_ctype AS
(
column_1 int4,
column_2 varchar(100),
column_3 varchar(500)
)
Then create a funcction :
CREATE
OR
REPLACE
FUNCTION PUBLIC.getStudents
()
RETURNS SETOF students_data_ctype AS $BODY$ DECLARE res
students_data_ctype;
BEGIN
FOR res IN
SELECT
column_1,
column_2,
column_3
FROM
STUDENTS
LOOP RETURN NEXT res;
END LOOP;
END
; $BODY$ LANGUAGE 'plpgsql'
GO
Function call :
Select * FROM getStudents()
Taddaaa! You will get your data.
I am trying to create a view inside the function using plpgsql which returns the x column of the "small" table which is defined as (x integer,y integer).
create or replace function skyline_naive2(dataset text) returns setof integer as
$$
declare
fullx text;
begin
fullx = dataset||'_skyline_naive2';
execute format('create view %s as select x,y from %s',fullx,dataset);
return query select x from fullx;
end
$$ language plpgsql;
select * from skyline_naive2('small');
It returns "relation fullx does not exist"
I understand that it is because there is no fullx relation, but I want to call the view using the variable name.
Any help will be
Use dynamic SQL for select (as you have used for create):
create or replace function skyline_naive2(dataset text) returns setof integer as
$$
declare
fullx text;
begin
fullx = dataset||'_skyline_naive2';
execute format('create view %I as select x,y from %I',fullx,dataset);
return query execute format('select x from %I', fullx);
end
$$ language plpgsql;
You need to EXECUTE your dynamic query:
RETURN QUERY EXECUTE 'SELECT x FROM ' || fullx;
Trying to create a function that given the name of a table will create a function with the table name concatenated to _myView
eg if the name of the table is students the function will create a view called students_myView
Here's what I have so far.
create or replace function skyline_naive(tableName text)
as $$
declare
name text;
begin
name:= $1;
create or replace view name_myView as select * from name;
end
$$ language plpgsql;
A dynamic command in PLPgSQL must be executed as a string with EXECUTE statement.
To make it work, you should write it like this:
create or replace function skyline_naive(tableName text)
returns void as $$
begin
execute format('create or replace view %1$s_myView as select * from %1$s;', tableName)
return;
end;
$$ language
plpgsql;
I am trying to create a function that returns a SELECTed resultset.
When I call my postgres function like this select * from tst_dates_func() I get an error as shown below:
ERROR: query has no destination for result data
HINT: If you want to discard the results of a SELECT, use PERFORM instead.
CONTEXT: PL/pgSQL function "tst_dates_func" line 3 at SQL statement
********** Error **********
ERROR: query has no destination for result data
SQL state: 42601
Hint: If you want to discard the results of a SELECT, use PERFORM instead.
Context: PL/pgSQL function "tst_dates_func" line 3 at SQL statement
Here is the function I created:
CREATE OR REPLACE FUNCTION tst_dates_func()
RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$
BEGIN
select a.date_value, a.date_id, a.date_desc from dates_tbl a;
END;
$BODY$
LANGUAGE plpgsql;
I am not sure why I am getting the above error. I would like to run select * from tst_dates_func();
and get data back. Or further join the result set if needed. What is the problem here?
Do it as plain SQL
CREATE OR REPLACE FUNCTION tst_dates_func()
RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$
select a.date_value, a.date_id, a.date_desc from dates_tbl a;
$BODY$
LANGUAGE sql;
If you really need plpgsql use return query
CREATE OR REPLACE FUNCTION tst_dates_func()
RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$
BEGIN
perform SELECT dblink_connect('remote_db');
return query
select a.date_value, a.date_id, a.date_desc from dates_tbl a;
END;
$BODY$
LANGUAGE plpgsql;
In PLPGSQL - use RETURN QUERY
CREATE OR REPLACE FUNCTION tst_dates_func()
RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$
BEGIN
RETURN QUERY (select a.date_value, a.date_id, a.date_desc from dates_tbl a);
END;
$BODY$
LANGUAGE plpgsql;
I couldn't do it as plain SQL as I needed to enter some data into a database for further processing and wanted to create a variable. Or at least I did not figure out the correct syntax for that. And the accepted answer had code I did not need, such as connecting to the database, as I ran this from inside pgAdmin with a connection setup already. I also had to drop the function when I made edits to it.
I was using this for inserting a geometry for intersection. A different use case and example could help someone else. This also shows how to then view this data and use it just like a table.
-- Get a geojson shape inside of postgres for further use
DROP FUNCTION fun();
CREATE OR REPLACE FUNCTION fun()
RETURNS TABLE (geometry geometry) AS
$BODY$
DECLARE geojson TEXT;
BEGIN
geojson := '{
"type":"Polygon",
"coordinates":[[[-90.9516399548092,39.8942337977775],[-90.9513913202472,39.8936939306154],[-90.9522805177147,39.8937108246505],[-90.9549542293894,39.8937616571416],[-90.954948768846,39.8945506794343],[-90.9531755591848,39.894492766522],[-90.9531770788457,39.8942868819087],[-90.9516399548092,39.8942337977775]]],
"crs":{"type":"name","properties":{"name":"EPSG:4326"}},
}';
return query (SELECT ST_GeomFromGeoJSON(geojson) AS geometry);
END;
$BODY$
LANGUAGE plpgsql;
-- View test insert
SELECT * FROM fun()