For using the MonetDB-rmath extension, I was interested in using table-returning functions to return multiple values. Is there a fast and elegant way to combine the results with the source table in SQL? To make this concrete, consider some test data and a function to calculate a 95% confidence interval from a mean and standard error: drop table test; create table test as select cast(value as double) as value from generate_series(0,5); drop function cis(double,double); create function cis(mu double, se double) returns table(lci double, uci double) begin return select mu-1.96*se, mu+1.96*se; end; We can then call the table-returning function: select * from cis((select value, 1.0 from test)); If we want to re-join the results with the source table, we could use row_number() or use lateral: -- Using row_number: select * from (select *, row_number() over() as rid from test) as t1 natural join (select *, row_number() over() as rid from cis((select value,1.0 from test))) as t2; -- Using lateral: select * from test, lateral cis(test.value, cast(1.0 as double)) as t2; I believe that the latter will lead to a slow loop, even when BAT functions are available. The table-returning function can be used in the select statement only for a scalar expression: select cis(0,1).*; -- ok select cis(0,1).* from test; -- Error: no such operator 'cis' select cis(value,1).* from test; -- Error: identifier 'value' unknown Again, is there a fast and elegant way to combine the source table with a table-returning function in SQL? Kindly, Mark.