TableA
Id imge
-- ----
1 1.jpeg
2 2.jpeg
1 1.jpeg
1 1.jpeg
o/p needed
id image
------------
1 1.jpeg
1.jpeg
1.jpeg
I created a function,
create or replace function(vid in integer,vimg out varchar) returns setof record as
$$
declare
im varchar;
begin
select image into im from tablea wher id=$1;
return query
select im;
$$
end;
plpgsql
But it's not working. I need to retrieve the images without using the arrays and loops.
You are declaring your function as setof record meaning that it will return any number of rows spanning. You need to redeclare the function and change internal select's to match returning type.
Or I'm wrong and I just miss what you are trying to do.
I think simple function like this is better to write in language sql instead of plpgsql:
create or replace function func(vid in integer)
returns table(vimg varchar)
as
$$
select imge from tablea where id=$1;
$$ language sql;
Anyway, to return multiple records from function your can return either table or setof record.
sql fiddle demo
You might be looking for GROUP_CONCAT()
SELECT GROUP_CONCAT(imge) as images
FROM TableA GROUP BY Id;
Oh I missed. You were in PostgreSQL, huh?
No worries. There is an equivalent for group_concat in PostgreSQL: array_agg
SELECT id, array_agg(imge)
FROM TableA GROUP BY Id;
Related
I'm new to databases and SQL and i've been messing around with functions on POSTGRESQL and I made a simple function to select all names from a table.
But the function, when called, returns just a single row as opposed to all rows being returned when i use SELECT c_name FROM customers; instead of the code shown below:
CREATE OR REPLACE FUNCTION get_cust_names()
RETURNS varchar AS
$body$
SELECT c_name FROM customers;
$body$
LANGUAGE SQL
Function call
SELECT get_cust_names()
this returns just a SINGLE row and this isnt code that i will use in a project etc. I'm just curious as to why postgresql behaves this way.
You need to declare the function as returns table(..) or returns setof
CREATE OR REPLACE FUNCTION get_cust_names()
RETURNS table(cust_name varchar)
AS
$body$
SELECT c_name
FROM customers;
$body$
LANGUAGE SQL;
Then use it like a table:
select *
from get_cust_names();
I have a table that looks like this:
CREATE TABLE label (
hid UUID PRIMARY KEY DEFAULT UUID_GENERATE_V4(),
name TEXT NOT NULL UNIQUE
);
I want to create a function that takes a list of names and inserts multiple rows into the table, ignoring duplicate names, and returns an array of the IDs generated for the rows it inserted.
This works:
CREATE OR REPLACE FUNCTION insert_label(nms TEXT[])
RETURNS UUID[]
AS $$
DECLARE
ids UUID[];
BEGIN
CREATE TEMP TABLE tmp_names(name TEXT);
INSERT INTO tmp_names SELECT UNNEST(nms);
WITH new_names AS (
INSERT INTO label(name)
SELECT tn.name
FROM tmp_names tn
WHERE NOT EXISTS(SELECT 1 FROM label h WHERE h.name = tn.name)
RETURNING hid
)
SELECT ARRAY_AGG(hid) INTO ids
FROM new_names;
DROP TABLE tmp_names;
RETURN ids;
END;
$$ LANGUAGE PLPGSQL;
I have many tables with the exact same columns as the label table, so I would like to have a function that can insert into any of them. I'd like to create a dynamic query to do that. I tried that, but this does not work:
CREATE OR REPLACE FUNCTION insert_label(h_tbl REGCLASS, nms TEXT[])
RETURNS UUID[]
AS $$
DECLARE
ids UUID[];
query_str TEXT;
BEGIN
CREATE TEMP TABLE tmp_names(name TEXT);
INSERT INTO tmp_names SELECT UNNEST(nms);
query_str := FORMAT('WITH new_names AS ( INSERT INTO %1$I(name) SELECT tn.name FROM tmp_names tn WHERE NOT EXISTS(SELECT 1 FROM %1$I h WHERE h.name = tn.name) RETURNING hid)', h_tbl);
EXECUTE query_str;
SELECT ARRAY_AGG(hid) INTO ids FROM new_names;
DROP TABLE tmp_names;
RETURN ids;
END;
$$ LANGUAGE PLPGSQL;
This is the output I get when I run that function:
psql=# select insert_label('label', array['how', 'now', 'brown', 'cow']);
ERROR: syntax error at end of input
LINE 1: ...SELECT 1 FROM label h WHERE h.name = tn.name) RETURNING hid)
^
QUERY: WITH new_names AS ( INSERT INTO label(name) SELECT tn.name FROM tmp_names tn WHERE NOT EXISTS(SELECT 1 FROM label h WHERE h.name = tn.name) RETURNING hid)
CONTEXT: PL/pgSQL function insert_label(regclass,text[]) line 19 at EXECUTE
The query generated by the dynamic SQL looks like it should be exactly the same as the query from static SQL.
I got the function to work by changing the return value from an array of UUIDs to a table of UUIDs and not using CTE:
CREATE OR REPLACE FUNCTION insert_label(h_tbl REGCLASS, nms TEXT[])
RETURNS TABLE (hid UUID)
AS $$
DECLARE
query_str TEXT;
BEGIN
CREATE TEMP TABLE tmp_names(name TEXT);
INSERT INTO tmp_names SELECT UNNEST(nms);
query_str := FORMAT('INSERT INTO %1$I(name) SELECT tn.name FROM tmp_names tn WHERE NOT EXISTS(SELECT 1 FROM %1$I h WHERE h.name = tn.name) RETURNING hid', h_tbl);
RETURN QUERY EXECUTE query_str;
DROP TABLE tmp_names;
RETURN;
END;
$$ LANGUAGE PLPGSQL;
I don't know if one way is better than the other, returning an array of UUIDs or a table of UUIDs, but at least I got it to work one of those ways. Plus, possibly not using a CTE is more efficient, so it may be better to stick with the version that returns a table of UUIDs.
What I would like to know is why the dynamic query did not work when using a CTE. The query it produced looked like it should have worked.
If anyone can let me know what I did wrong, I would appreciate it.
... why the dynamic query did not work when using a CTE. The query it produced looked like it should have worked.
No, it was only the CTE without (required) outer query. (You had SELECT ARRAY_AGG(hid) INTO ids FROM new_names in the static version.)
There are more problems, but just use this query instead:
INSERT INTO label(name)
SELECT unnest(nms)
ON CONFLICT DO NOTHING
RETURNING hid;
label.name is defined UNIQUE NOT NULL, so this simple UPSERT can replace your function insert_label() completely.
It's much simpler and faster. It also defends against possible duplicates from within your input array that you didn't cover, yet. And it's safe under concurrent write load - as opposed to your original, which might run into race conditions. Related:
How to use RETURNING with ON CONFLICT in PostgreSQL?
I would just use the simple query and replace the table name.
But if you still want a dynamic function:
CREATE OR REPLACE FUNCTION insert_label(_tbl regclass, _nms text[])
RETURNS TABLE (hid uuid)
LANGUAGE plpgsql AS
$func$
BEGIN
RETURN QUERY EXECUTE format(
$$
INSERT INTO %s(name)
SELECT unnest($1)
ON CONFLICT DO NOTHING
RETURNING hid
$$, _tbl)
USING _nms;
END
$func$;
If you don't need an array as result, stick with the set (RETURNS TABLE ...). Simpler.
Pass values (_nms) to EXECUTE in a USING clause.
The tablename (_tbl) is type regclass, so the format specifier %I for format() would be wrong. Use %s instead. See:
Table name as a PostgreSQL function parameter
In PostgreSQL 11 database I have table with 6 column. Next function return static number of defined columns.
CREATE FUNCTION CALCULATION(INTEGER)
RETURNS TABLE(
ORGANIZATION_ID INT4,
ORGANIZATION_NAME VARCHAR,
ORGANIZATION_RANG INT4,
PARENT_ORGANIZATION_ID INT4,
PARENT_ORGANIZATION_NAME VARCHAR,
PARENT_ORGANIZATION_RANG INT4
) AS $$
SELECT * FROM ANALYTICS;
$$ LANGUAGE SQL;
How can I make an SQL function in Postgres 11 which return a result set with dynamic number of columns according to a parameter passed in?
For example if I call SELECT * FROM CALCULATION(2);, function return first 2 columns.
If this is not possible with an SQL function, is it possible with a PL/pgSQL function?
This is possible for RECORD returning functions.
CREATE FUNCTION calculation(how_many integer) RETURNS SETOF RECORD
LANGUAGE plpgsql
AS $fff$
BEGIN
IF how_many = 1
THEN RETURN QUERY SELECT 'foo'::text;
ELSIF how_many = 2
THEN RETURN QUERY SELECT 'foo'::text, 'bar'::text;
END IF;
END;
$fff$
;
And now you can do:
jbet=> SELECT * FROM calculation(1) AS f(first_col text);
first_col
-----------
foo
(1 row)
jbet=> SELECT * FROM calculation(2) AS f(first_col text, second_col text);
first_col | second_col
-----------+------------
foo | bar
(1 row)
The very serious downside is that each time you call the function you have to define set of returned columns, so I don't think you'll find this answer useful : )
Anyway, Postgresql needs to know returned type of each SELECT before it runs the query, so one or other way you have to define the columns.
JSON return value could be a reasonable answer if you just want the data and don't care if there are separate columns or not.
Backing up a step, why not use a standard select to get the columns you want from your set-returning function?
select organization_name,
organization_rang,
parent_organization_name,
parent_organization_rang
from calculation();
That's easy to follow and flexible. I'm guessing that you've written a simplified example and have a good reason for what you're asking...but I figured I'd double-check.
I want this postgres function to work :
CREATE OR REPLACE FUNCTION difference_of_match_ids_in_match_history_and_match_results()
returns table(match_id BIGINT)
as
$$
BEGIN
return QUERY
SELECT *
FROM sports.match_history
WHERE match_id NOT IN (SELECT match_id
FROM sports.match_results);
END $$
LANGUAGE 'plpgsql';
This stand alone query works just fine:
SELECT *
FROM sports.match_history
WHERE match_id NOT IN (SELECT match_id FROM sports.match_results);
But when I put it into this function and try to run it like this:
select *
from difference_of_match_ids_in_match_history_and_match_results();
I get this:
SQL Error [42702]: ERROR: column reference "match_id" is ambiguous
Detail: It could refer to either a PL/pgSQL variable or a table
column. Where: PL/pgSQL function
difference_of_match_ids_in_match_history_and_match_results() line 3 at
RETURN QUERY
I've seen other questions with this same error, and they suggest naming the sub queries to specify which instance of a column you're referring to, however, those examples use joins and my query works fine outside of the function.
If I do need to name the column, how would I do so with only one sub-query?
If that isn't the issue, then I'm assuming that there's something wrong with the way I'm defining a function.
You query is fine. The ambiguity is on the match_id in returns table(match_id BIGINT) rename it or prefix the columns with the table name in your query
CREATE OR REPLACE FUNCTION difference_of_match_ids_in_match_history_and_match_results()
returns table(new_name BIGINT)
as
$$
BEGIN
return QUERY
SELECT *
FROM sports.match_history
WHERE match_id NOT IN (SELECT match_id
FROM sports.match_results);
END $$
LANGUAGE 'plpgsql';
or
CREATE OR REPLACE FUNCTION difference_of_match_ids_in_match_history_and_match_results()
returns table(match_id BIGINT)
as
$$
BEGIN
return QUERY
SELECT sports.match_history.match_id
FROM sports.match_history
WHERE sports.match_history.match_id NOT IN (SELECT sports.match_results.match_id
FROM sports.match_results);
END $$
LANGUAGE 'plpgsql';
Didn't test the code.
The structure of the result set must match the function result type. If you want to get only match_ids:
CREATE OR REPLACE FUNCTION difference_of_match_ids_in_match_history_and_match_results()
RETURNS TABLE(m_id BIGINT) -- !!
AS
$$
BEGIN
RETURN QUERY
SELECT match_id -- !!
FROM sports.match_history
WHERE match_id NOT IN (SELECT match_id
FROM sports.match_results);
END $$
LANGUAGE 'plpgsql';
If you want to get whole rows as a result:
DROP FUNCTION difference_of_match_ids_in_match_history_and_match_results();
CREATE OR REPLACE FUNCTION difference_of_match_ids_in_match_history_and_match_results()
RETURNS SETOF sports.match_history -- !!
AS
$$
BEGIN
RETURN QUERY
SELECT * -- !!
FROM sports.match_history
WHERE match_id NOT IN (SELECT match_id
FROM sports.match_results);
END $$
LANGUAGE 'plpgsql';
As others have answerd, it's an ambiguity between the result definition and PL/pgSQL variables. The column name in a set returning function is in fact also a variable inside the function.
But you don't need PL/pgSQL for this in the first place. If you use a plain SQL function it will be more efficient and the problem will go away as well:
CREATE OR REPLACE FUNCTION difference_of_match_ids_in_match_history_and_match_results()
returns table(match_id BIGINT)
as
$$
SELECT match_id --<< do not return * - only return one column
FROM sports.match_history
WHERE match_id NOT IN (SELECT match_id
FROM sports.match_results);
$$
LANGUAGE sql;
Note that the language name is an identifier and should not be quoted at all.
The naming conflict between column names and plpgsql OUT parameters has been addressed. More details here:
Postgresql - INSERT RETURNING INTO ambiguous column reference
I would also use a different query style. NOT IN (SELECT ...) is typically slowest and carries traps with NULL values. Use NOT EXISTS instead:
SELECT match_id
FROM sports.match_history h
WHERE NOT EXISTS (
SELECT match_id
FROM sports.match_results
WHERE match_id = h.match_id
);
More:
Select rows which are not present in other table
Is it possible to pass the results of a postgres query as an input into another function?
As a very contrived example, say I have one query like
SELECT id, name
FROM users
LIMIT 50
and I want to create a function my_function that takes the resultset of the first query and returns the minimum id. Is this possible in pl/pgsql?
SELECT my_function(SELECT id, name FROM Users LIMIT 50); --returns 50
You could use a cursor, but that very impractical for computing a minimum.
I would use a temporary table for that purpose, and pass the table name for use in dynamic SQL:
CREATE OR REPLACE FUNCTION f_min_id(_tbl regclass, OUT min_id int) AS
$func$
BEGIN
EXECUTE 'SELECT min(id) FROM ' || _tbl
INTO min_id;
END
$func$ LANGUAGE plpgsql;
Call:
CREATE TEMP TABLE foo ON COMMIT DROP AS
SELECT id, name
FROM users
LIMIT 50;
SELECT f_min_id('foo');
Major points
The first parameter is of type regclass to prevent SQL injection. More info in this related answer on dba.SE.
I made the temp table ON COMMIT DROP to limit its lifetime to the current transaction. May or may not be what you want.
You can extend this example to take more parameters. Search for code examples for dynamic SQL with EXECUTE.
-> SQLfiddle demo
I would take the problem on the other side, calling an aggregate function for each record of the result set. It's not as flexible but can gives you an hint to work on.
As an exemple to follow your sample problem:
CREATE OR REPLACE FUNCTION myMin ( int,int ) RETURNS int AS $$
SELECT CASE WHEN $1 < $2 THEN $1 ELSE $2 END;
$$ LANGUAGE SQL STRICT IMMUTABLE;
CREATE AGGREGATE my_function ( int ) (
SFUNC = myMin, STYPE = int, INITCOND = 2147483647 --maxint
);
SELECT my_function(id) from (SELECT * FROM Users LIMIT 50) x;
It is not possible to pass an array of generic type RECORD to a plpgsql function which is essentially what you are trying to do.
What you can do is pass in an array of a specific user defined TYPE or of a particular table row type. In the example below you could also swap out the argument data type for the table name users[] (though this would obviously mean getting all data in the users table row).
CREATE TYPE trivial {
"ID" integer,
"NAME" text
}
CREATE OR REPLACE FUNCTION trivial_func(data trivial[])
RETURNS integer AS
$BODY$
DECLARE
BEGIN
--Implementation here using data
return 1;
END$BODY$
LANGUAGE 'plpgsql' VOLATILE;
I think there's no way to pass recordset or table into function (but I'd be glad if i'm wrong). Best I could suggest is to pass array:
create or replace function my_function(data int[])
returns int
as
$$
select min(x) from unnest(data) as x
$$
language SQL;
sql fiddle demo