I am trying to implement a function that returns a table with the same structure as an input table in the parameter, using PL/pgSQL (PostgreSQL 9.3). Basically, I want to update a table, and return a copy of the updated table with plpgsql. I searched around SO and found several related questions (e.g. Return dynamic table with unknown columns from PL/pgSQL function and Table name as a PostgreSQL function parameter), which lead to the following minimal test example:
CREATE OR REPLACE FUNCTION change_val(_lookup_tbl regclass)
RETURNS _lookup_tbl%rowtype AS --problem line
$func$
BEGIN
RETURN QUERY EXECUTE format('UPDATE %s SET val = 2 RETURNING * ; ', _lookup_tbl);
END
$func$ LANGUAGE plpgsql;
But I can't get past giving the correct return type for TABLE or SETOF RECORD in the problem line. According to this answer:
SQL demands to know the return type at call time
But I think the return type (which I intend to borrow from the input table type) is known. Can some one help explain if it is possible to fix the signature of the above PL/pgSQL function?
Note, I need to parametrize the input table and return the update of that table. Alternatives are welcome.
What you have so far looks good. The missing ingredient: polymorphic types.
CREATE OR REPLACE FUNCTION change_val(_tbl_type anyelement)
RETURNS SETOF anyelement -- problem solved
LANGUAGE plpgsql AS
$func$
BEGIN
RETURN QUERY EXECUTE format(
'UPDATE %s SET val = 2 RETURNING *;'
, pg_typeof(_tbl_type))
);
END
$func$;
Call (important):
SELECT * FROM change_val(NULL::some_tbl);
db<>fiddle here
Old sqlfiddle
See (last paragraph):
Refactor a PL/pgSQL function to return the output of various SELECT queries
Related
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 show_emp_details(character varying) line 5 at SQL statement
SQL state: 42601
mycode:
CREATE OR REPLACE function show_emp_details(project_id varchar(10))
RETURNS VARCHAR
LANGUAGE 'plpgsql'
AS $BODY$
DECLARE
show_emp_details VARCHAR;
BEGIN
SELECT emp_id ,role_id,from_date,to_date
FROM allocation al
JOIN t_project pj
ON(pj.project_id=al.project_id);
RETURN
emp_id ,role_id,from_date,to_date ;
END
$BODY$;
drop function show_emp_details();
SELECT show_emp_details('P01');
I need to create a functions
There are multiple problems with your function:
You declare it to return single varchar field but based on your function body you are trying returning multiple fields. Take a look at Return multiple fields as a record in PostgreSQL with PL/pgSQL
You have SELECT in your function, but it does not have INTO, you do not define where the result should be put. If you wish to return the result of the SQL take a look at https://www.postgresql.org/docs/current/plpgsql-control-structures.html#PLPGSQL-STATEMENTS-RETURNING - especially at RETURN QUERY.
You don't even need plpgsql for a simple function returning query result. Use sql language for it.
I'm sure you aren't selecting the function after you drop it, just edit the code in your question.
I'm trying to build a parametrized view using a postgres function:
CREATE FUNCTION schemaB.testFunc(p INT)
RETURNS TABLE
AS
RETURN (SELECT * FROM schemaZ.mainTable WHERE id=p)
The problem is always the same:
SQL Error [42601]: ERROR: syntax error at or near "AS"
Any idea on what could I be doing wrong?
You need to specify the columns of the "return table", this is either done using
returns table(col_1 integer, col_2 text, ...)
In your case you are returning only rows of one table, so it's easier to use
returns setof maintable
As documented in the manual the function body needs to be enclosed in single quotes, or using dollar quoting.
As stored functions can be written in many different languages in Postgres, you also need to specify a language - in this case language sql is suitable.
So putting all that together, you need:
CREATE FUNCTION schemaB.testFunc(p_id INT)
RETURNS setof schemaZ.mainTable
AS
$$
SELECT *
FROM schemaZ.mainTable
WHERE id = p_id
$$
language sql;
A return statement is not required for language sql functions.
I'm trying to store a simple SELECT query with the new CREATE PROCEDURE method in PostgreSQL 11. My idea is to store the queries in the DB, because I can have a much simple code in my API server and maybe I don't need to develop a query builder if I can use if/else in an sql function with enforced type safety. I have this minimal example:
First I tried this plpgsql function:
CREATE OR REPLACE PROCEDURE test_proc() AS $$
BEGIN
SELECT * FROM my_db
LIMIT 1;
END;
$$ LANGUAGE plpgsql;
CALL test_proc();
However throws this error:
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 test_proc() line 3 at SQL statement SQL state: 42601
If I trying to use RETURN QUERY:
CREATE OR REPLACE PROCEDURE test_proc() AS $$
BEGIN
RETURN QUERY;
SELECT * FROM my_db
LIMIT 1;
END;
$$ LANGUAGE plpgsql;
I'm getting this error:
ERROR: cannot use RETURN QUERY in a non-SETOF function
LINE 17: RETURN QUERY; ^
SQL state: 42804
Character: 310
I'm also getting error when I try to use RETURNS void AS $$ or RETURNS table(...) AS $$. Seems like RETURNS not supported in CREATE PROCEDURE? So, is it possible to return a table with the new stored procedure method? Or if it's not, maybe JSON?
Procedures in PostgreSQL (Oracle, DB2) are not same like procedures in MS-SQL. It has different target, and you cannot use it. Usually, the best what you can do, forgot all what you know from MSSQL. The procedural part is really different.
Only functions can returns some data - so you need to use functions. Functions can returns scalar value, composite value or array value, or table. You want function that returns table.
CREATE OR REPLACE FUNCTION fx()
RETURNS SETOF mytab AS $$
BEGIN
RETURN QUERY SELECT * FROM mytab;
END
$$ LANGUAGE plpgsql;
SELECT * FROM fx();
For record:
You can use SQL function, that can have better (or worse) performance (depends on context). These functions are sometimes named as parametrized views.
CREATE OR REPLACE FUNCTION fx()
RETURNS SETOF mytab AS $$
SELECT * FROM mytab;
$$ LANGUAGE sql;
Attention: this technique is antipattern!!! Don't do it. It is really not good idea. The functions should not to wrap queries. If you want to hide some complexity of queries, then use a views. Don't use a functions. Functions are effective barier for query optimizer, and when you use this antipattern, then optimizer cannot to well optimize any non trivial queries that use in this form evaluated subqueries.
Use it - if you want very very slow applications - or if your data model or queries are primitive. In other cases, don't do it.
Don't afraid of SQL - it is great language designed for manual usage. It is good to place all data access to one module (model), to don't access database everywhere in your code, but it is bad too hide SQL in your code.
First of all Procedure was introduced in PostgreSQL 11, If you are using below 11th version, you cannot use Procedures. Instead to Procedure you can use functions.
Syntax to create function
CREATE or replace function function_name(_parameter varchar)
returns table(col1 varchar, col2 varchar, col3 varchar)
language 'plpgsql'
as $BODY$
BEGIN
return query select a.col1, a.col2, b.col3 from table a
join table2 as b on a.col1 = b.col1;
END;
$BODY$;
you can call a function same a like table
select * From function_name('sample data');
syntax to create Procedure.
CREATE OR REPLACE PROCEDURE procedure_name(_parameter varcar,INOUT result refcursor)
LANGUAGE 'plpgsql'
AS $BODY$
BEGIN
open result for SELECT , * from sampletable where a = _parameter;
END;
$BODY$;
you can execute a Procedure using call keyword, within a transaction
BEGIN;
CALL public.procedure_name( 'sample data', 'test');
fetch all in "test";
COMMIT;
The postgreSql 11. we have to create a stored procedure
there is the solution :
Create procedure to execute query in PostgreSQL
I need to show the Tree_Nodes table data
CREATE OR REPLACE FUNCTION sample()
RETURNS TABLE() AS
$BODY$
BEGIN
select * from "Tree_Nodes";
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100
ROWS 1000;
ALTER FUNCTION sample()
OWNER TO postgres;
It fails with:
ERROR: query has no destination for result data
Avoid the error and i will get the table column format in all data
To return the result of a SELECT, a pure SQL function is much more suitable:
CREATE OR REPLACE FUNCTION sample()
RETURNS TABLE ( .... ) AS
$BODY$
select * from "Tree_Nodes";
$BODY$
LANGUAGE sql;
Or if you really need PL/pgSQL, you need to use return query (which is clearly documented in the manual)
CREATE OR REPLACE FUNCTION sample()
RETURNS TABLE (....)
AS
$BODY$
BEGIN
return query select * from "Tree_Nodes";
END;
$BODY$
LANGUAGE plpgsql;
But you cannot just specify returns table() you have to also define the structure of the result:
CREATE OR REPLACE FUNCTION sample()
RETURNS TABLE(id integer, some_column text, other_column decimal(10,2), ...)
AS
The exact error you quote is caused by using SELECT without an INTO clause in PL/PgSQL. You must either use SELECT INTO somevariable, use RETURN QUERY, if you want to discard the data, use the PERFORM statement instead of SELECT, as covered by the PL/PgSQL manual.
Once you fix that by using RETURN QUERY SELECT .... you'll find that the function still doesn't work, because RETURNS TABLE() doesn't make sense. You're returning an empty result set. It'll fail, complaining that the statement is returning a result set that doesn't match the function.
It makes no sense to do this anyway, since you can just write it as a trivial SQL function like:
CREATE OR REPLACE FUNCTION sample()
RETURNS SETOF "Tree_Nodes"
AS $$
SELECT * FROM "Tree_Nodes";
$$ LANGUAGE sql;
This function appears to serve no purpose. What are you trying to achieve with it?
(By the way, you should generally avoid SELECT * in production code. List the columns. That way, if you add a column later, things that use the table won't suddenly stop working.)
I want a plpgsql function that returns the content of any table, given the name. The function below, although not working because of many reasons will gove you the general idea. Safety and coding practice aside, what's the easiest way to accomplish this?
In the end I want to get these results trough a Java CallableStatement.
CREATE OR REPLACE FUNCTION get_table(tablename VARCHAR)
RETURNS SETOF RECORD AS $PROC$
BEGIN
RETURN QUERY SELECT * FROM tablename;
END;
$PROC$ LANGUAGE 'plpgsql';
You can get your function working like this:
CREATE OR REPLACE FUNCTION get_table(tablename VARCHAR)
RETURNS SETOF RECORD AS $PROC$
BEGIN
RETURN QUERY EXECUTE 'SELECT * FROM ' || quote_ident(tablename);
END;
$PROC$ LANGUAGE 'plpgsql';
In order to call it, you must specify names and data types for all returned columns. If you want to list table "t" which has two columns, you could use your function like this:
SELECT * FROM get_table('t') x(id int, val text);
Which of course, is longer and a lot more trouble than either:
SELECT * FROM t;
or the equivalent:
TABLE t;
I really can't imagine a use-case where such a function makes anything better.