So I have a function in PostgreSQL that dynamically selects columns from a dynamic table. I got this solution from this post and it works great other than one thing.
This is inside of a file that is connected to a Node server, and so the $1 and $2 in the second SELECT * FROM represent values passed from there. The issue right now is that I am getting a syntax error that I don't understand (I am newer to SQL so that may be why).
$2 represents the name of the table to be selected from as a string, so for example it could be 'goals'. The error is syntax error at or near "'goals'". I realize that it cannot be a string with single quotes (I believe) and so I am wondering how to convert that variable to be a table name? using "goals" there as well as goals, for example works as expected, though I'm not sure how to do that outside of a function.
CREATE OR REPLACE FUNCTION get_data(user_id INT, table_name anyelement)
RETURNS SETOF ANYELEMENT AS $$
BEGIN
RETURN QUERY EXECUTE
format('SELECT * FROM %s WHERE user_id = $1', pg_typeof(table_name)) USING user_id;
END;
$$ LANGUAGE plpgsql;
SELECT * FROM get_data($1, NULL::$2);
$1 is 5 and $2 is 'goals' for example
After many hours of trying to figure it out, thanks to Adrian's comment, I found MassiveJS (how I'm connecting to my PostgreSQL server) has inline functions to do queries. In my controller file in my server I was able to create a one line function as such:
const data = await db[tableName].where("user_id=$1", [userId])
Didn't know inline SQL existed in MassiveJS, so that was great to find out!
Related
I would love to exploit the SQL output formatting of PostgreSQL inside my PL/pgSQL functions, but I'm starting to feel I have to give up the idea.
I have my PL/pgSQL function query_result:
CREATE OR REPLACE FUNCTION query_result(
this_query text
) RETURNS SETOF record AS
$$
BEGIN
RETURN QUERY EXECUTE this_query;
END;
$$ LANGUAGE plpgsql;
..merrily returning a SETOF records from an input text query, and which I can use for my SQL scripting with dynamic queries:
mydb=# SELECT * FROM query_result('SELECT ' || :MYVAR || ' FROM Alice') AS t (id int);
id
----
1
2
3
So my hope was to find a way to deliver this same nicely formatted output from inside a PL/pgSQL function instead, but RAISE does not support SETOF types, and there's no magic predefined cast from SETOF records to text (I know I could create my own CAST..)
If I create a dummy print_result function:
CREATE OR REPLACE FUNCTION print_result(
this_query text
) RETURNS void AS
$$
BEGIN
SELECT query_result(this_query);
END;
$$ LANGUAGE plpgsql;
..I cannot print the formatted output:
mydb=# SELECT print_result('SELECT ' || :MYVAR || ' FROM Alice');
ERROR: set-valued function called in context that cannot accept a set
...
Thanks for any suggestion (which preferably works with PostgreSQL 8.4).
Ok, to do anything with your result set in print_result you'll have to loop over it. That'll look something like this -
Here result_record is defined as a record variable. For the sake of explanation, we'll also assume that you have a formatted_results variable that is defined as text and defaulted to a blank string to hold the formatted results.
FOR result_record IN SELECT * FROM query_result(this_query) AS t (id int) LOOP
-- With all this, you can do something like this
formatted_results := formatted_results ||','|| result_record.id;
END LOOP;
RETURN formatted_results;
So, if you change print_results to return text, declare the variables as I've described and add this in, your function will return a comma-separated list of all your results (with an extra comma at the end, I'm sure you can make use of PostgreSQL's string functions to trim that). I'm not sure this is exactly what you want, but this should give you a good idea about how to manipulate your result set. You can get more information here about control structures, which should let you do pretty much whatever you want.
EDIT TO ANSWER THE REAL QUESTION:
The ability to format data tuples as readable text is a feature of the psql client, not the PostgreSQL server. To make this feature available in the server would require extracting relevant code or modules from the psql utility and recompiling them as a database function. This seems possible (and it is also possible that someone has already done this), but I am not familiar enough with the process to provide a good description of how to do that. Most likely, the best solution for formatting query results as text will be to make use of PostgreSQL's string formatting functions to implement the features you need for your application.
Edit: After posting I found Erwin Brandstetter's answer to a similar question. It sounds like in 9.2+ I could use the last option he listed, but none of the other alternatives sound workable for my situation. However, the comment from Jakub Kania and reiterated by Craig Ringer suggesting I use COPY, or \copy, in psql appears to solve my problem.
My goal is to get the results of executing a dynamically created query into a text file.
The names and number of columns are unknown; the query generated at run time is a 'pivot' one, and the names of columns in the SELECT list are taken from values stored in the database.
What I envision is being able, from the command line to run:
$ psql -o "myfile.txt" -c "EXECUTE mySQLGeneratingFuntion(param1, param2)"
But what I'm finding is that I can't get results from an EXECUTEd query unless I know the number of columns and their types that are in the results of the query.
create or replace function carrier_eligibility.createSQL() returns varchar AS
$$
begin
return 'SELECT * FROM carrier_eligibility.rule_result';
-- actual procedure writes a pivot query whose columns aren't known til run time
end
$$ language plpgsql
create or replace function carrier_eligibility.RunSQL() returns setof record AS
$$
begin
return query EXECUTE carrier_eligibility.createSQL();
end
$$ language plpgsql
-- this works, but I want to be able to get the results into a text file without knowing
-- the number of columns
select * from carrier_eligibility.RunSQL() AS (id int, uh varchar, duh varchar, what varchar)
Using psql isn't a requirement. I just want to get the results of the query into a text file, with the column names in the first row.
What format of a text file do you want? Something like csv?
How about something like this:
CREATE OR REPLACE FUNCTION sql_to_csv(in_sql text) returns setof text
SECURITY INVOKER -- CRITICAL DO NOT CHANGE THIS TO SECURITY DEFINER
LANGUAGE PLPGSQL AS
$$
DECLARE t_row RECORD;
t_out text;
BEGIN
FOR t_row IN EXECUTE in_sql LOOP
t_out := t_row::text;
t_out := regexp_replace(regexp_replace(t_out, E'^\\(', ''), E'\\)$', '');
return next t_out;
END LOOP;
END;
$$;
This should create properly quoted csv strings without the header. Embedded newlines may be a problem but you could write a quick Perl script to connect and write the data or something.
Note this presumes that the tuple structure (parenthesized csv) does not change with future versions, but it currently should work with 8.4 at least through 9.2.
I'm trying to iterate over the result of a query using a record data type. Nevertheless, if I try to access one column using the table alias defined in the query, I get the following error:
ERRO: schema "inv_row" does not exist
CONTEXT: SQL command "SELECT inv_row.s.processor <> inv_row.d.processor"
PL/pgSQL function "teste" line 7 at IF
Here is the code that throws this error:
CREATE OR REPLACE FUNCTION teste() returns void as $$
DECLARE
inv_row record;
BEGIN
FOR inv_row in SELECT * FROM sa_inventory s LEFT JOIN dim_inventory d ON s.macaddr = d.macaddr LOOP
IF inv_row.s.processor <> inv_row.d.processor THEN
<do something>;
END IF;
END LOOP;
END;
$$ language plpgsql;
Is there another way to access a column of a particular table inside a record data type?
Fortunately the answer here is relatively simple. You have to use parentheses to indicate tuples:
IF (inv_row.s).processor <> (inv_row.d).processor THEN
This is because SQL specifies meaning to the depth of the namespaces and therefore without this PostgreSQL cannot safely determine what this means. So inv_row.s.processor means the processor column of the s table in the inv_row schema. However (inv_row.s).processor means take the s column of the inf_row table, treat it as a tuple, and take the processor column of that.
I was attempting to use Dynamic SQL to run some queries in postgres.
Example:
EXECUTE format('SELECT * from result_%s_table', quote_ident((select id from ids where condition = some_condition)))
I have to query a table, which is of the form result_%s_table wherein, I need to substitute the correct table name (an id) from an another table.
I get the error ERROR: prepared statement "format" does not exist
Link: string substitution with query result postgresql
EXECUTE ... USING only works in PL/PgSQL - ie within functions or DO blocks written in the PL/PgSQL language. It does not work in plain SQL; the EXECUTE in plain SQL is completely different, for executing prepared statements. You cannot use dynamic SQL directly in PostgreSQL's SQL dialect.
Compare:
PL/PgSQL's EXECUTE ... USING; to
SQL's EXECUTE
See the 2nd last par in my prior answer.
In addition to not running except in PL/PgSQL your SQL statement is wrong, it won't do what you expect. If (select id from ids where condition = some_condition) returns say 42, the statement would fail if id is an integer. If it's cast to text you'd get:
EXECUTE format('SELECT * from result_%s_table', quote_ident('42'));
EXECUTE format('SELECT * from result_%s_table', '"42"');
EXECUTE 'SELECT * from result_"42"_table';
That's invalid. You actually want result_42_table or "result_42_table". You'd have to write something more like:
EXECUTE format('SELECT * from %s', quote_ident('result_'||(select id from ids where condition = some_condition)||'_table'))
... if you must use quote_ident.
CREATE OR REPLACE FUNCTION public.exec(
text)
RETURNS SETOF RECORD
LANGUAGE 'plpgsql'
AS $BODY$
BEGIN
RETURN QUERY EXECUTE $1 ;
END
$BODY$;
usage:
select * from exec('select now()') as t(dt timestamptz)
Try using
RETURN QUERY EXECUTE '<SQL Command>'
This will return data into form of table. You have to use this into stored function of PostgreSQL.
I have already created on full demonstration on custom filter and custom sorting using dynamic query of PostgreSQL.
Please visit this url:
http://www.dbrnd.com/2015/05/postgresql-dynamic-sql/
These all look more complicated than the OP's question. A different formatting should do the trick.. but it could absolutely the case that I don't understand.
From how I read OP's question, I think others in a similar situation may benefit from how I got it.
I am using Postgre on Redshift, and I ran into this issue and found a solution.
I was trying to create a dynamic query, putting in my own date.
date = dt.date(2018, 10, 30)
query = ''' select * from table where date >= ''' + str(my_date) + ''' order by date '''
But, the query entirely ignores the condition when typing it this way.
However, if you use the percent sign (%), you can insert the date correctly.
One correct way to write the above statement is:
query = ''' select * from table where date >= ''' + ''' '%s' ''' % my_date + ''' order by date '''
So, maybe this is helpful, or maybe it is not. I hope it helps at least one person in my situation!
Best wishes.
EXECUTE will work only on pl/pqsql environment.
instead of EXECUTE try with SELECT
SELECT format('SELECT * from result_%s_table', quote_ident((select id from ids where condition = some_condition))
output would be the dynamic query.
Basically, at least for proof of concept, I want a function where I can run:
SELECT res('table_name'); and this will give me the results of SELECT * FROM table_name;.
The issue I am having is schema...in the declaration of the function I have:
CREATE OR REPLACE FUNCTION res(table_name TEXT) RETURNS SETOF THISISTHEPROBLEM AS
The problem is that I do not know how to declare my return, as it wants me to specify a table or a schema, and I won't have that until the function is actually run.
Any ideas?
You can do this, but as mentioned before you have to add a column definiton list in the SELECT query.
CREATE OR REPLACE FUNCTION res(table_name TEXT) RETURNS SETOF record AS $$
BEGIN
RETURN QUERY EXECUTE 'SELECT * FROM ' || table_name;
END;
$$ LANGUAGE plpgsql;
SELECT * FROM res('sometable') sometable (col1 INTEGER, col2 INTEGER, col3 SMALLINT, col4 TEXT);
Why for any real practical purpose would you just want to pass in table and select * from it? For fun maybe?
You can't do it without defining some kind of known output like jack and rudi show. Or doing it like depesz does here using output parameters http://www.depesz.com/index.php/2008/05/03/waiting-for-84-return-query-execute-and-cursor_tuple_fraction/.
A few hack around the wall approachs are to issue raise notices in a loop and print out a result set one row at a time. Or you could create a function called get_rows_TABLENAME that has a definition for every table you want to return. Just use code to generate the procedures creations. But again not sure how much value doing a select * from a table, especially with no constraints is other than for fun or making the DBA's blood boil.
Now in SQL Server you can have a stored procedure return a dynamic result set. This is both a blessing and curse as you can't be certain what comes back without looking up the definition. For me I look at PostgreSQL's implementation to be the more sound way to go about it.
Even if you manage to do this (see rudi-moore's answer for a way if you have 8.4 or above), You will have to expand the type explicitly in the select - eg:
SELECT res('table_name') as foo(id int,...)