I have a function which generates a static SQL query and returns it as a string. What I need to do is to run the returned string as if I was typing it directly in psql. Here is a very simplified test case (the true mechanism is far more complicated but the following test case at least shows the idea)
drop table if exists person;
create table person(
first_name varchar(30),
last_name varchar(50),
email varchar(100)
);
insert into person(first_name, last_name, email) values
('fname01', 'lname01', 'fname01.lname01#hotmail.com'),
('fname02', 'lname02', 'fname02.lname02#hotmail.com'),
('fname03', 'lname03', 'fname03.lname03#hotmail.com'),
('fname04', 'lname04', 'fname04.lname04#hotmail.com'),
('fname05', 'lname05', 'fname05.lname05#hotmail.com');
--
--
drop function if exists sql_gen;
create function sql_gen() returns text as
$fun$
begin
return 'select * from person';
end;
$fun$
language plpgsql;
--
--
Now if I run the following:
select * from sql_gen();
sql_gen
----------------------
select * from person
(1 ligne)
This gives me the sql query. But what I want to do is to run the query from
the returned string as if I was writing manually select * from person in psql
and hitting Enter in order to obtain the result of the query.
I've checked PREPARE, EXECUTE on the online documentation but so far I've not been able to achieve this. Could you kindly make some clarification?
And answer specific for psql is to change your semicolon to \gexec.
select * from sql_gen() \gexec
Related
I have to write a stored procedure that starts copying the data from a table 'company' into a staging table 'company_stg' if no records for that date are present in it.
I have the following code :
CREATE OR REPLACE
PACKAGE BODY PKG_TEST AS
PROCEDURE SP_BILLING AS
BEGIN
EXECUTE IMMEDIATE 'SELECT * FROM COMPANY INTO COMPANY_STG
WHERE NOT EXISTS (SELECT * FROM COMPANY_STG WHERE AS_OF_DATE = "2023-02-08")';
END;
END PKG_TEST;
I AM GETTING THE ERROR "SQL COMMAND NOT PROPERLY ENDED"
company * company_stg have as_of_date as a column. rest all are same.
please help me with this
I have also tried
if not exists (SELECT * FROM COMPANY_STG WHERE AS_OF_DATE = "2023-02-08")
then
select from company into company_stg
So many things look bad in that piece of code...
First, why use dynamic SQL execute immediate? It's best to avoid dynamic SQL as much as possible because it leads to runtime errors and requires pretty much instrumentation so that it may be debugged. Generally you use dynamic SQL when you do not know beforehand the name of a table it will operate on, which is not the case for you. You definitely know you have to work with tables COMPANY and COMPANY_STG. Is it not so?
Then, it doesn't look like you have read the manual to see an insert select.
When you insert into a table, it's best to give the list of columns into which you actually insert data. If one alters that table and adds one or more than one column, the insert which does not have the list of columns will crash.
Thus, to insert into COMPANY_STG data from COMPANY, the SQL should look like below:
insert into company_stg(
... ---- here should be the list of columns you insert data into
)
select
... --- here should the source columns you are willing to insert
from company c
where not exists (
select 1
from company_stg cs
where cs.as_of_date= --- what is the condition??? I did not understand
)
;
You have not given the structures for those tables, so that I can't give you the columns to select and to insert into. Nor did I really understand what the condition for inserting data should be.
SELECT does not perform a copy and SELECT * FROM COMPANY INTO COMPANY_STG is not valid syntax. You want to use an INSERT statement to do that (and check if there is any row first):
CREATE OR REPLACE PACKAGE BODY PKG_TEST AS
PROCEDURE SP_BILLING
AS
BEGIN
DECLARE
v_staged_count NUMBER;
BEGIN
SELECT 1
INTO v_staged_count
FROM COMPANY_STG
WHERE AS_OF_DATE = DATE '2023-02-08'
FETCH FIRST ROW ONLY; -- We don't care how many rows so stop after finding
-- the first one.
-- Stop as rows have been found.
RETURN;
EXCEPTION
WHEN NO_DATA_FOUND THEN
-- Continue
NULL;
END;
INSERT INTO company_stg
SELECT *
FROM COMPANY;
END;
END PKG_TEST;
/
fiddle
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
I am trying to automate a set of sentences that I execute several times a day. For this I want to put them in a postgres function and just call the function to execute the sentences consecutively. If everything runs OK then in the end return the SUCCESS value. The following function replicates my idea and the error I am getting when executing the function:
CREATE OR REPLACE FUNCTION createTable() RETURNS int AS $$
BEGIN
DROP TABLE IF EXISTS MY_TABLE;
CREATE TABLE MY_TABLE
(
ID integer
)
WITH (
OIDS=FALSE
);
insert into MY_TABLE values(1);
select * from MY_TABLE;
RETURN 'SUCCESS';
END;
$$ LANGUAGE plpgsql;
Invocation:
select * from createTable();
With my ignorance of postgresql I would expect to obtain the SUCCESS value as a return (If everything runs without errors). But the returned message causes me confusion, isn't it the same as a function in any other programming language? When executing the function I get the following message:
query has no destination for result data Hint: If you want to
discard the results of a SELECT, use PERFORM instead.
query has no destination for result data Hint: If you want to discard the results of a SELECT, use PERFORM instead.
You are getting this error because you do not assign the results to any variable in the function. In a function, you would typically do something like this instead:
select * into var1 from MY_TABLE;
Therefore, your function would look something like this:
CREATE OR REPLACE FUNCTION createTable() RETURNS int AS $$
DECLARE
var1 my_table%ROWTYPE;
BEGIN
DROP TABLE IF EXISTS MY_TABLE;
CREATE TABLE MY_TABLE
(
ID integer
)
WITH (
OIDS=FALSE
);
insert into MY_TABLE values(1);
select * into var1 from MY_TABLE;
<do something with var1>
RETURN 'SUCCESS';
END;
$$ LANGUAGE plpgsql;
Otherwise, if you don't put the results into a variable, then you're likely hoping to achieve some side effect (like advancing a sequence or firing a trigger somehow). In that case, plpgsql expects you to use PERFORM instead of SELECT
Also, BTW your function RETURNS int but at the bottom of your definition you RETURN 'SUCCESS'. SUCCESS is a text type, not an int, so you will eventually get this error once you get past that first error message -- be sure to change it as necessary.
I have found this very interesting article: Refactor a PL/pgSQL function to return the output of various SELECT queries
from Erwin Brandstetter which describes how to return all columns of various tables with only one function:
CREATE OR REPLACE FUNCTION data_of(_table_name anyelement, _where_part text)
RETURNS SETOF anyelement AS
$func$
BEGIN
RETURN QUERY EXECUTE
'SELECT * FROM ' || pg_typeof(_table_name)::text || ' WHERE ' || _where_part;
END
$func$ LANGUAGE plpgsql;
Call:
SELECT * FROM data_of(NULL::tablename,'1=1 LIMIT 1');
This works pretty well. I need a very similar solution but for getting data from a table on a different database via dblink. That means the call NULL::tablename will fail since the table does not exists on the database where the call is made. I wonder how to make this work. Any try to connect inside of the function via dblink to a different database failed to get the result of NULL::tablename. It seems the polymorph function needs a polymorph parameter which creates the return type of the function implicit.
I would appreciate very much if anybody could help me.
Thanks a lot
Kind regards
Brian
it seems this request is more difficult to explain than I thought it is. Here is a second try with a test setup:
Database 1
First we create a test table with some data on database 1:
CREATE TABLE db1_test
(
id integer NOT NULL,
txt text
)
WITH (
OIDS=TRUE
);
INSERT INTO db1_test (id, txt) VALUES(1,'one');
INSERT INTO db1_test (id, txt) VALUES(2,'two');
INSERT INTO db1_test (id, txt) VALUES(3,'three');
Now we create the polymorph function on database 1:
-- create a polymorph function with a polymorph parameter "_table_name" on database 1
-- the return type is set implicit by calling the function "data_of" with the parameter "NULL::[tablename]" and a where part
CREATE OR REPLACE FUNCTION data_of(_table_name anyelement, _where_part text)
RETURNS SETOF anyelement AS
$func$
BEGIN
RETURN QUERY EXECUTE
'SELECT * FROM ' || pg_typeof(_table_name)::text || ' WHERE ' || _where_part;
END
$func$ LANGUAGE plpgsql;
Now we make test call if everything works as aspected on database 1
SELECT * FROM data_of(NULL::db1_test, 'id=2');
It works. Please notice I do NOT specify any columns of the table db1_test. Now we switch over to database 2.
Database 2
Here I need to make exactly the same call to data_of from database 1 as before and although WITHOUT knowing the columns of the selected table at call time. Unfortunatly this is not gonna work, the only call which works is something like that:
SELECT
*
FROM dblink('dbname=[database1] port=[port] user=[user] password=[password]'::text, 'SELECT * FROM data_of(NULL::db1_test, \'id=2\')'::text)
t1(id integer, txt text);
Conclusion
This call works, but as you can see, I need to specify at least once how all the columns look like from the table I want to select. I am looking for any way to bypass this and make it possible to make a call WITHOUT knowing all of the columns from the table on database 1.
Final goal
My final goal is to create a function in database 2 which looks like
SELECT * from data_of_dblink('table_name','where_part')
and which calls internaly data_of() on database1 to make it possible to select a table on a different database with a where part as parameter. It should work like a static view but with the possiblity to pass a where part as parameter.
I am extremly open for suggestions.
Thanks a lot
Brian
It may look like a duplicate of existing questions (e.g. This one) but they only deal with passing "new" arguments, not selecting rows from the database.
I have a table, for example:
CREATE TABLE my_table (
id bigserial NOT NULL,
name text,
CONSTRAINT my_table_pkey PRIMARY KEY (id)
);
And a function:
CREATE FUNCTION do_something(row_in my_table) RETURNS void AS
$$
BEGIN
-- does something
END;
$$
LANGUAGE plpgsql;
I would like to run it on data already existing in the database. It's no problem if I would like to use it from another PL/pgSQL stored procedure, for example:
-- ...
SELECT * INTO row_var FROM my_table WHERE id = 123; -- row_var is of type my_table%rowtype
PERFORM do_something(row_var);
-- ...
However, I have no idea how to do it using an "ordinary" query, e.g.
SELECT do_something(SELECT * FROM my_table WHERE id = 123);
ERROR: syntax error at or near "SELECT"
LINE 1: SELECT FROM do_something(SELECT * FROM my_table ...
Is there a way to execute such query?
You need to pass a scalar record to that function, this requires to enclose the actual select in another pair of parentheses:
SELECT do_something( (SELECT * FROM my_table WHERE id = 123) );
However the above will NOT work, because the function only expects a single column (a record of type my_table) whereas select * returns multiple columns (which is something different than a single record with multiple fields).
In order to return a record from the select you need to use the following syntax:
SELECT do_something( (SELECT my_table FROM my_table WHERE id = 123) );
Note that this might still fail if you don't make sure the select returns exactly one row.
If you want to apply the function to more than one row, you can do that like this:
select do_something(my_table)
from my_table;