I would like to execute a SQL statement based on a string. I have created the SQL statement through a function which returns a string. Can anybody explain how I can execute the statement that is returned? I know that you can't do it in plain SQL, so I was thinking about putting it in a function. The only issue is that the columns in the statement aren't always the same, so I don't know which data types to use for the columns. I'm using Postgres 9.1.0.
For example, suppose the SQL string returned from my function the is:
Select open, closed, discarded from abc
But, it can also be:
Select open from abc
Or
Select open, closed from abc
How can I execute any of these strings, so that the results would be returned as a table with only the columns listed in the statement?
Edit: the function is written in PL/pgSQL. And the results will be used for reporting where they don't want to see columns that have no values. So the function that I wrote returns the names of all columns that have values and then add it to the SQL statement.
Thanks for your help!
I don't think you can return the rows directly from a function, because its return type would be unknown. Even if you specified the return type as RECORD, you'd have to list the returned columns at call time. Based on Wayne Conrad's idea, you could do this:
CREATE FUNCTION my_create(cmd TEXT) RETURNS VOID AS $$
BEGIN
EXECUTE 'CREATE TEMPORARY TABLE temp_result AS ' || cmd;
END;
$$ VOLATILE LANGUAGE plpgsql;
Then use the function like this:
BEGIN;
SELECT my_create(...);
SELECT * FROM temp_result;
ROLLBACK; -- or COMMIT
Related
Basically i want to split the string based on the delimiter for example :-
"this,is,foo" should return this is foo i.e; without the comma into separate records .
i am trying to use pgadmin 4 version 2.
this is my sample code below that i want in function dialog :-
create or replace function STRING_SPLIT(str text,delimiter character)
return SET OF record;
as
begin
return QUERY SELECT trim(a)
FROM unnest(string_to_array('john,smith,jones', ',')) AS a; //str, delim
end
i am basically trying to insert the expanded row array into set of records.
i tried creating table and return it in the return statement but could not specify the column name in function dialog of pgadmin also i could not find "set of record" return type in the same dialog box?
can anyone help?
In almost all cases, using returns table() is the better solution.
create or replace function STRING_SPLIT(str text,delimiter character)
return table(word text) --<< no ; here!!
as
$$ --<< you need quotes around the body
SELECT trim(a) as word
FROM unnest(string_to_array(text, delimiter)) AS t(a);
$$
language sql; --<< no PL/pgSQL required, SQL is enough
If you do want to use setof record then you always have to specify the column names when using the function:
create or replace function STRING_SPLIT(str text,delimiter character)
return setof record
as
$$ --<< you need quotes around the body
SELECT trim(a) as word
FROM unnest(string_to_array(text, delimiter)) AS t(a);
$$
language sql; --<< no PL/pgSQL required, SQL is enough
Then:
select *
from string_split('foo,bar',',') as t(word);
However, Postgres already has a built-in function for this:
select *
from regexp_split_to_table('foo,bar',',') as t(word);
Though this post is older, but needs to post an answer here. So it will help people like me. As I was looking for the same and found the answer.
in pgAdmin4 'setof' is not present in the return type. While creating function in pgAdmin using create function window, you need to select record as a return type.
Then click on the options and set "Returns a set?" to "Yes". like this
Then it will automatically take setof record as a return type and will show in code in sql viwer, but not in return type selected.
Then it will automatically take setof record as a return type and will show in code in sql viwer, but not in return type selected.
I have tables that contain the same type of data for every year, but the data gathered varies slightly in that they may not have the same fields.
d_abc_2016
d_def_2016
d_ghi_2016
d_jkl_2016
There are certain constants for each table: company_id, employee_id, salary.
However, each one might or might not have these fields that are used to calculate total incentives: bonus, commission, cash_incentives. There are a lot more, but just using these as a examples. All numeric
I should note at this point, users only have the ability to run SELECT statements.
What I would like to be able to do is this:
Give the user the ability to call in SELECT and specify their own fields in addition to the call
Pass the table name being used into the function to use in conditional logic to determine how the query string should be constructed for the eventual total_incentives calculation in addition to passing the whole table so a ton of arguments don't have to be passed into the function
Basically this:
SELECT employee_id, salary, total_incentives(t, 'd_abc_2016')
FROM d_abc_2016 t;
So the function being called will calculate total_incentives which is numeric for that employee_id and also show their salary. But the user might choose to add other fields to look at.
For the function, because the fields used in the total_incentives function will vary from table to table, I need to create logic to construct the query string dynamically.
CREATE OR REPLACE FUNCTION total_incentives(ANYELEMENT, t text)
RETURNS numeric AS
$$
DECLARE
-- table name lower case in case user typed wrong
tbl varchar(255) := lower($2;
-- parse out the table code to use in conditional logic
tbl_code varchar(255) := split_part(survey, '_', 2);
-- the starting point if the query string
base_calc varchar(255) := 'salary + '
-- query string
query_string varchar(255);
-- have to declare this to put computation INTO
total_incentives_calc numeric;
BEGIN
IF tbl_code = 'abc' THEN
query_string := base_calc || 'bonus';
ELSIF tbl_code = 'def' THEN
query_string := base_calc || 'bonus + commission';
ELSIF tbl_code = 'ghi' THEN
-- etc...
END IF;
EXECUTE format('SELECT $1 FROM %I', tbl)
INTO total_incentives_calc
USING query_string;
RETURN total_incentives_calc;
END;
$$
LANGUAGE plpgsql;
This results in an:
ERROR: invalid input syntax for type numeric: "salary + bonus"
CONTEXT: PL/pgSQL function total_incentives(anyelement,text) line 16 at EXECUTE
Since it should be returning a set of numeric values. Change it to the following:
CREATE OR REPLACE FUNCTION total_incentives(ANYELEMENT, t text)
RETURNS SETOF numeric AS
$$
...
RETURN;
Get the same error.
Figure well, maybe it is a table it is trying to return.
CREATE OR REPLACE FUNCTION total_incentives(ANYELEMENT, t text)
RETURNS TABLE(tot_inc numeric) AS
$$
...
Get the same error.
Really, any variation produces that result. So really not sure how to get this to work.
Look at RESULT QUERY, RESULT NEXT, or RESULT QUERY EXECUTE.
https://www.postgresql.org/docs/9.6/static/plpgsql-control-structures.html
RESULT QUERY won't work because it takes a hard coded query from what I can tell, which won't take in variables.
RESULT NEXT iterates through each record, which I don't think will be suitable for my needs and seems like it will be really slow... and it takes a hard coded query from what I can tell.
RESULT QUERY EXECUTE sounds promising.
-- EXECUTE format('SELECT $1 FROM %I', tbl)
-- INTO total_incentives_calc
-- USING query_string;
RETURN QUERY
EXECUTE format('SELECT $1 FROM %I', tbl)
USING query_string;
And get:
ERROR: structure of query does not match function result type
DETAIL: Returned type character varying does not match expected type numeric in column 1.
CONTEXT: PL/pgSQL function total_incentives(anyelement,text) line 20 at RETURN QUERY
It should be returning numeric.
Lastly, I can get this to work, but it won't be DRY. I'd rather not make a bunch of separate functions for each table with duplicative code. Most of the working examples I have seen have the whole query in the function and are called like such:
SELECT total_incentives(d_abc_2016, 'd_abc_2016');
So any additional columns would have to be specified in the function as:
EXECUTE format('SELECT employee_id...)
Given the users will only be able to run SELECT in query this really isn't an option. They need to specify any additional columns they want to see inside a query.
I've posted a similar question but was told it was unclear, so hopefully this lengthier version will more clearly explain what I am trying to do.
The column names and tables names should not be used as query parameters passed by USING clause.
Probably lines:
RETURN QUERY
EXECUTE format('SELECT $1 FROM %I', tbl)
USING query_string;
should be:
RETURN QUERY
EXECUTE format('SELECT %s FROM %I', query_string, tbl);
This case is example why too DRY principle is sometimes problematic. If you write it directly, then your code will be simpler, cleaner and probably shorter.
Dynamic SQL is one from last solution - not first. Use dynamic SQL only when your code will be significantly shorter with dynamic sql than without dynamic SQL.
I would like to use a plpgsql function with a table and several columns as input parameter. The idea is to split the table in chunks and do something with each part.
I tried the following function:
CREATE OR REPLACE FUNCTION my_func(Integer)
RETURNS SETOF my_part
AS $$
DECLARE
out my_part;
BEGIN
FOR i IN 0..$1 LOOP
FOR out IN
SELECT * FROM my_func2(SELECT * FROM table1 WHERE id = i)
LOOP
RETURN NEXT out;
END LOOP;
END LOOP;
RETURN;
END;
$$
LANGUAGE plpgsql;
my_func2() is the function that does some work on each smaller part.
CREATE or REPLACE FUNCTION my_func2(table1)
RETURNS SETOF my_part2 AS
$$
BEGIN
RETURN QUERY
SELECT * FROM table1;
END
$$
LANGUAGE plpgsql;
If I run:
SELECT * FROM my_func(99);
I guess I should receive the first 99 IDs processed for each id.
But it says there is an error for the following line:
SELECT * FROM my_func2(select * from table1 where id = i)
The error is:
The subquery is only allowed to return one column
Why does this happen? Is there an easy way to fix this?
There are multiple misconceptions here. Study the basics before you try advanced magic.
Postgres does not have "table variables". You can only pass 1 column or row at a time to a function. Use a temporary table or a refcursor (like commented by #Daniel) to pass a whole table. The syntax is invalid in multiple places, so it's unclear whether that's what you are actually trying.
Even if it is: it would probably be better to process one row at a time or rethink your approach and use a set-based operation (plain SQL) instead of passing cursors.
The data types my_part and my_part2 are undefined in your question. May be a shortcoming of the question or a problem in the test case.
You seem to expect that the table name table1 in the function body of my_func2() refers to the function parameter of the same (type!) name, but this is fundamentally wrong in at least two ways:
You can only pass values. A table name is an identifier, not a value. You would need to build a query string dynamically and execute it with EXECUTE in a plpgsql function. Try a search, many related answers her on SO. Then again, that may also not be what you wanted.
table1 in CREATE or REPLACE FUNCTION my_func2(table1) is a type name, not a parameter name. It means your function expects a value of the type table1. Obviously, you have a table of the same name, so it's supposed to be the associated row type.
The RETURN type of my_func2() must match what you actually return. Since you are returning SELECT * FROM table1, make that RETURNS SETOF table1.
It can just be a simple SQL function.
All of that put together:
CREATE or REPLACE FUNCTION my_func2(_row table1)
RETURNS SETOF table1 AS
'SELECT ($1).*' LANGUAGE sql;
Note the parentheses, which are essential for decomposing a row type. Per documentation:
The parentheses are required here to show that compositecol is a column name not a table name
But there is more ...
Don't use out as variable name, it's a keyword of the CREATE FUNCTION statement.
The syntax of your main query my_func() is more like psudo-code. Too much doesn't add up.
Proof of concept
Demo table:
CREATE TABLE table1(table1_id serial PRIMARY KEY, txt text);
INSERT INTO table1(txt) VALUES ('a'),('b'),('c'),('d'),('e'),('f'),('g');
Helper function:
CREATE or REPLACE FUNCTION my_func2(_row table1)
RETURNS SETOF table1 AS
'SELECT ($1).*' LANGUAGE sql;
Main function:
CREATE OR REPLACE FUNCTION my_func(int)
RETURNS SETOF table1 AS
$func$
DECLARE
rec table1;
BEGIN
FOR i IN 0..$1 LOOP
FOR rec IN
SELECT * FROM table1 WHERE table1_id = i
LOOP
RETURN QUERY
SELECT * FROM my_func2(rec);
END LOOP;
END LOOP;
END
$func$ LANGUAGE plpgsql;
Call:
SELECT * FROM my_func(99);
SQL Fiddle.
But it's really just a a proof of concept. Nothing useful, yet.
As the error log is telling you.. you can return only one column in a subquery, so you have to change it to
SELECT my_func2(SELECT Specific_column_you_need FROM hasval WHERE wid = i)
a possible solution can be that you pass to funct2 the primary key of the table your funct2 needs and then you can obtain the whole table by making the SELECT * inside the function
I'm using the squirrel sql client to work with Postgres and the problem is that the same query returns different results.
If a query below execute as is, it works fine:
select foo.column1 as Field1, 1 as Field2 from (values (3343),(45323)) as Foo
But if the query execute from stored function like this one:
CREATE OR REPLACE FUNCTION getSomeData(text) RETURNS setof tmp_stub_type AS
$body$
DECLARE
r tmp_stub_type%rowtype;
BEGIN
FOR r IN
select foo.column1 as Field1, 1 as Field2 from (values (3343),(45323)) as Foo
LOOP
RETURN NEXT r;
END LOOP;
RETURN;
END;
$body$
LANGUAGE 'plpgsql';
It returns the same rows count but with UnknownType values with one field instead two.
tmp_stub_type is normal table with two integer fields and nothing more.
I tried to solve it by the Postgres pgAdmin, but he showed me the same thing except the values - they was right but placed in one field and separated by comma.
I need run the query inside stored function, please help deal with it and sorry for my english.
i'm using: Postgres 9.3, Squirrel 3.5.3, OS Windows
To get multiple columns from a function that returns a row type or has multiple output parameters, use e.g. SELECT * FROM getSomeData(...) instead of SELECT getSomeData(...).
Source: http://www.postgresql.org/docs/9.3/static/plpgsql-control-structures.html#AEN58217
Below is one function which has one query ,
Now I want to convert into dynamic query. I want one table name parameter so query return data from multiple tables.
please help me in this I am new in PostgreSQL , Thanks in Advance !
create or replace function GetEmployees()
returns setof weather as
'select * from weather;'
language 'sql';
This is basic PL/PgSQL. Use PL/PgSQL's EXECUTE .. USING statement and format function with the %I format-specifier.
create or replace function get_sometable(tablename regclass)
returns setof whatever_type as
BEGIN
RETURN QUERY EXECUTE format('select * from %I";', tablename);
END;
language 'plpgsql';
This will only work if all tablenames you might pass return compatible result types, as occurs with partitioning. Otherwise you'll have to return SETOF RECORD and then pass the table layout in the function invocation. See the documentation for a discussion of RECORD and SETOF RECORD.
Look into RETURNS TABLE as another convenient alternative for when the table types aren't compatible but you can still return a compatible subset via a suitable SELECT list.
If you're doing table partitioning, you should really do it as the PostgreSQL documentation on table partitioning advises, using table inheritance and triggers.
(Elaborating on Convert SQL Server stored procedure into PostgreSQL stored procedure)