[Original] PostgreSQL returns multiple result sets

Source: Internet
Author: User

MySQL stored procedures can easily return multiple result sets at a time, but POSTGRESQL currently does not provide such a function.

A literal translation method is to use a cursor, but you can also put the result set in an array or a large temporary table or XML format for output.


For example, you can simply write a stored procedure in MySQL.


Delimiter | create procedure sp_get_multiple_set1 () begin select * from j1 limit 20; select * from tmp_2 limit 20; end; | delimiter; two result sets are obtained after execution. T_girl -- call sp_get_multiple_set1 (); + ------ + | id | str1 | + ------ + | 1 | love | 2 | hate | + ------ + 2 rows in set (0.00 sec) + ------ + ------------- + | id | register_date | + ------ + --------------- + | 1 | 2014-01-18 | 2 | 2014-01-03 | 3 | 2014-01-16 | + ------ + --------------- + 3 rows in set (0.00 sec) query OK, 0 rows affected (0.00 sec) t_girl --



In the PostgreSQL environment, the following function code can only be implemented with a cursor, and cannot be returned in the function.


create or replace function sp_get_multiple_set1(IN f_id int,refcursor,refcursor) returns setof refcursoras$ytt$declare r1 alias for $2;               r2 alias for $3;begin   open  r1 for select * from j1 where id =f_id;   return next r1;   open r2 for select * from tmp_2 where id = f_id;   return next r2;end;$ytt$ language plpgsql;


Next, you can obtain the corresponding cursor result set in a transaction.


t_girl=# begin;BEGINt_girl=# select * from sp_get_multiple_set1(1,'a'::refcursor,'b'::refcursor); sp_get_multiple_set1---------------------- a b(2 rows)t_girl=# fetch all from a; id | str1----+------  1 | love(1 row)t_girl=# fetch all from b; id | register_date----+---------------  1 | 2013-01-20(1 row)t_girl=# close a;CLOSE CURSORt_girl=# close b;CLOSE CURSORt_girl=# commit;COMMITt_girl=#


If multiple result sets exist, but each result set contains only one row of data, you can also use the OUT parameter.


create or replace function sp_get_single_set2(f_id int,IN refcursor,IN refcursor,OUT r3 ytt_j1,OUT r4 ytt_tmp_2) returns  recordas$ytt$declare r1 alias for $2;              r2 alias for $3;begin   open  r1 for select * from j1 where id =f_id;   open r2 for select * from tmp_2 where id = f_id;   loop      fetch r1 into r3;      fetch r2 into r4;      exit when not found;      return;   end loop;   close r1;   close r2;end;$ytt$ language plpgsql;t_girl=# select * from sp_get_multiple_set2(1,'a'::refcursor,'b'::refcursor);    r3    |       r4      ----------+---------------- (1,love) | (1,2013-01-20)(1 row)t_girl=#

If the fields and types of multiple returned result sets are the same, the same result set will be followed.



Related Article

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.