问题
I created a stored procedure in PostgreSQL 11 to perform CRUD operation, and it works fine for 1. Create 2. Update 3. Delete, but while I run read command by passing Condition = 4 to select a result set, I get below error.
I have used PostgreSQL function to get result set it works for me, but I need to get result using the PostgreSQL stored procedure.
Here is my code for stored procedure:
CREATE OR REPLACE PROCEDURE public.testSpCrud(
fnam text,
lnam text,
id integer,
condition integer)
LANGUAGE 'plpgsql'
AS $BODY$
declare
countOfDisc int;
BEGIN
if condition=1 then
INSERT INTO public.employee(
employeeid, lname, fname, securitylevel, employeepassword, hphonearea, hphone, cphonearea, cphone, street, city, state, zipcode, extzip, name, email, groomerid, type, commission, inactive, carrierid, notoallemployees, languageid, isdogwalker, ispetsitter, ismobilegroomer, ssma_timestamp)
VALUES (4, 'Test', 'Test', 2, 2, 32, 32, 32, 32, 32, 32,32, 32, 32, 22, 22, 2, 2, 2, false, 223,true, 223, true, true, true, '2019-08-27');
end if;
if condition =2 then
delete from Employee where employeeid=id;
end if;
if condition =3 then
update Employee set fname='Test' where employeeid=id;
end if;
if condition =4 then
Select * from Employee;
end if;
END;
$BODY$;
ERROR: query has no destination for result data HINT: If you want to discard the results of a SELECT, use PERFORM instead. CONTEXT: PL/pgSQL function testspcrud(text,text,integer,integer) line 22 at SQL statement SQL state: 42601
回答1:
As of Postgres 12 it's not possible to return anything directly from a procedure.
Most likely, you fell for the widespread misnomer "stored procedure" and really want a function instead, which can return a value, a row or a set according to its declaration.
- In PostgreSQL, what is the difference between a “Stored Procedure” and other types of functions?
- How to return result of a SELECT inside a function in PostgreSQL?
Would work like this:
CREATE OR REPLACE FUNCTION public.testSpCrud(
fnam text,
lnam text,
id integer,
condition integer)
RETURNS SETOF Employee LANGUAGE plpgsql AS
$func$
BEGIN
CASE condition
WHEN 1 THEN
INSERT INTO public.employee(
employeeid, lname, fname, securitylevel, employeepassword, hphonearea, hphone, cphonearea, cphone, street, city, state, zipcode, extzip, name, email, groomerid, type, commission, inactive, carrierid, notoallemployees, languageid, isdogwalker, ispetsitter, ismobilegroomer, ssma_timestamp)
VALUES (4, 'Test', 'Test', 2, 2, 32, 32, 32, 32, 32, 32,32, 32, 32, 22, 22, 2, 2, 2, false, 223,true, 223, true, true, true, '2019-08-27');
WHEN 2 THEN
DELETE FROM Employee WHERE employeeid=id;
WHEN 3 THEN
UPDATE Employee SET fname='Test' WHERE employeeid=id;
WHEN 4 THEN
RETURN QUERY
SELECT * FROM Employee;
ELSE
RAISE EXCEPTION 'Unexpected condition value %!', condition;
END CASE;
END
$func$;
Simplified with a CASE construct while being at it, and added an ELSE clause. Adapt to your needs.
Call with:
SELECT * FROM public.testSpCrud(...);
Aside: all variable names of a plpgsql block are visible inside nested SQL DML commands. A variable named id is a problem waiting to happen. I suggest a safer naming convention, and / or table-qualify all column names in DML statements. One popular naming convention is to prepend variable names with an underscore. Like: _id.
And consider legal, lower-case identifiers in SQL and PL/pgSQL.
- Are PostgreSQL column names case-sensitive?
回答2:
Most people will suggest that when migrating MS SQL Server stored procedures to PostgreSQL, if the procedure returns a set of data (rows and columns), you change the stored procedure into a function, since functions, by nature, return sets of data. However, as of Postgres 11, you can return result sets from a PostgreSQL Procedure using cursors, though it can be tedious to iterate over the results.
The following demonstrates how to return a set of data from a PostgreSQL procedure using an INOUT cursor:
CREATE OR REPLACE PROCEDURE test_get_data_single(
_itemID int,
INOUT _message text = '',
INOUT _result_one refcursor = 'rs_resultone',
INOUT _returnCode text = '')
LANGUAGE plpgsql
AS
$$
BEGIN
_message := 'Test message for item ' || COALESCE(_itemID, 0);
_returnCode := '';
open _result_one for
SELECT *
FROM (values (1,2,3, 'fruit', current_timestamp - INTERVAL '5 seconds'),
(4,5,6, 'veggie', current_timestamp)) as t(a,b,c,d,e);
END;
$$;
To use, call the procedure within a transaction
BEGIN;
CALL test_get_data_single(1);
FETCH ALL FROM "rs_resultone";
COMMIT;
PostgreSQL also supports using Begin / End:
BEGIN;
CALL test_get_data_single(2);
FETCH ALL FROM "rs_resultone";
END;
Example results from DBeaver
+--------------------------+--------------+-------------+
| _message | _result_one | _returncode |
+--------------------------+--------------+-------------+
| Test message for item 2 | rs_resultone | |
+--------------------------+--------------+-------------+
+---+---+---+--------+---------------------|
| a | b | c | d | e |
+---+---+---+--------+---------------------|
| 1 | 2 | 3 | fruit | 2020-02-15 10:12:09 |
| 4 | 5 | 6 | veggie | 2020-02-15 10:12:09 |
+---+---+---+--------+---------------------|
For more advanced handling of the results, use an anonymous code block to iterate over the results
DO
$$
DECLARE
_message text = '';
_returnCode text = '';
_result_one refcursor;
_result_single refcursor;
_currentRow record;
_i int;
BEGIN
CALL test_get_data_single(1, _message => _message, _result_one => _result_single, _returnCode => _returnCode);
RAISE info 'Cursor _result_single from test_get_data_single: %', _result_single;
_i := 0;
WHILE TRUE
Loop
FETCH NEXT FROM _result_single INTO _currentRow;
IF _currentRow IS NULL Then
EXIT;
END IF;
_i := _i + 1;
RAISE info '%, array: %', _i, _currentRow;
RAISE info '%, values: % % % %', _i, _currentRow.a, _currentRow.b, _currentRow.c, _currentRow.d;
END LOOP;
End
$$;
Example results from DBeaver (look in the Server Output, opened with Ctrl+Shift+O):
Cursor _result_single from test_get_data_single: <unnamed portal 261>
1, array: (1,2,3,fruit,"2020-02-14 17:19:29.612822-08")
1, values: 1 2 3 fruit
2, array: (4,5,6,veggie,"2020-02-14 17:19:34.612822-08")
2, values: 4 5 6 veggie
Example results from psql:
INFO: Cursor _result_single from test_get_data_single: <unnamed portal 4>
INFO: 1, array: (1,2,3,fruit,"2020-02-14 17:22:50.81671-08")
INFO: 1, values: 1 2 3 fruit
INFO: 2, array: (4,5,6,veggie,"2020-02-14 17:22:55.81671-08")
INFO: 2, values: 4 5 6 veggie
A procedure can also return two result sets, using separate refcursor arguments:
CREATE OR REPLACE PROCEDURE test_get_data(
_itemID int,
INOUT _message TEXT = '',
INOUT _result_one refcursor = 'rs_resultone',
INOUT _result_two refcursor = 'rs_resulttwo',
INOUT _returnCode TEXT = '')
LANGUAGE plpgsql
AS
$$
BEGIN
_message := 'Test message for item ' || COALESCE(_itemID, 0);
_returnCode := '';
open _result_one for
SELECT *
FROM (values (1,2,3, 'fruit', current_timestamp - INTERVAL '5 seconds'), (4,5,6, 'veggie', current_timestamp)) as t(a,b,c,d,e);
open _result_two for
SELECT *
FROM (values ('one'), ('two'), ('three'), ('four')) as p(name);
END;
$$;
Retrieve results with:
BEGIN;
CALL test_get_data(1);
FETCH ALL FROM "rs_resultone";
FETCH ALL FROM "rs_resulttwo";
END;
Or use an expanded anonymous code block for viewing the results
DO
$$
DECLARE
_message text = '';
_returnCode text = '';
_result_one refcursor;
_result_two refcursor;
_result_single refcursor;
_currentRow record;
_i int;
BEGIN
CALL test_get_data(1, _message => _message, _result_one => _result_one, _result_two => _result_two, _returnCode => _returnCode);
RAISE info '%', _message;
RAISE info '';
RAISE info 'Cursor _result_one: %', _result_one;
_i := 0;
WHILE TRUE
Loop
FETCH NEXT FROM _result_one INTO _currentRow;
IF _currentRow IS NULL Then
EXIT;
END IF;
_i := _i + 1;
RAISE info '%, array: %', _i, _currentRow;
RAISE info '%, values: % % % %', _i, _currentRow.a, _currentRow.b, _currentRow.c, _currentRow.d;
END LOOP;
RAISE info '';
RAISE info 'Cursor _result_two: %', _result_two;
_i := 0;
WHILE TRUE
Loop
FETCH NEXT FROM _result_two INTO _currentRow;
IF _currentRow IS NULL Then
EXIT;
END IF;
_i := _i + 1;
RAISE info '%: %', _i, _currentRow;
END LOOP;
End
$$;
Output:
Test message for item 1
Cursor _result_one: <unnamed portal 263>
1, array: (1,2,3,fruit,"2020-02-14 17:25:06.528551-08")
1, values: 1 2 3 fruit
2, array: (4,5,6,veggie,"2020-02-14 17:25:11.528551-08")
2, values: 4 5 6 veggie
Cursor _result_two: <unnamed portal 264>
1: (one)
2: (two)
3: (three)
4: (four)
The alternative design pattern, especially for procedures that normally add/update data, but for where you occasionally want to preview results is to use RAISE INFO statements. For example:
If _infoOnly <> 0 Then
_infoHead := format('%-22s %-15s %-20s %-25s %-25s',
'State Change Preview',
'Parameter Name',
'Manager Name',
'Manager Type',
'Enabled (control_from_website=1)'
);
RAISE INFO '%', _infoHead;
FOR _previewData IN
SELECT PV.value || ' --> ' || _newValue AS State_Change_Preview,
PT.param_name AS Parameter_Name,
M.mgr_name AS manager_name,
MT.mgr_type_name AS Manager_Type,
M.control_from_website
FROM mc.t_param_value PV
INNER JOIN mc.t_param_type PT
ON PV.type_id = PT.param_id
INNER JOIN mc.t_mgrs M
ON PV.mgr_id = M.mgr_id
INNER JOIN mc.t_mgr_types MT
ON M.mgr_type_id = MT.mgr_type_id
INNER JOIN TmpManagerList U
ON M.mgr_name = U.manager_name
WHERE PT.param_name = 'mgractive' AND
PV.value <> _newValue AND
MT.mgr_type_active > 0
LOOP
_infoData := format('%-22s %-15s %-20s %-25s %-25s',
_previewData.State_Change_Preview,
_previewData.Parameter_Name,
_previewData.manager_name,
_previewData.Manager_Type,
_previewData.control_from_website
);
RAISE INFO '%', _infoData;
END LOOP;
_message := format('Would set %s managers to %s; see the Output window for details',
_countToUpdate,
_activeStateDescription);
Example usage (complete procedure is in the PNNL-Comp-Mass-Spec/DBSchema_PgSQL_DMS repo on GitHub):
CALL mc.EnableDisableManagers(
_enable => 1,
_managerTypeID => 11,
_managerNameList => 'Pub-80%',
_infoOnly => 1,
_includeDisabled => 0
);
Example results:
+-----------------------------------+-------------+
| _message | _returnCode |
+-----------------------------------+-------------+
| Would set 8 managers to Active; | |
| see the Output window for details | |
+-----------------------------------+-------------+
Output window contents:
State Change Preview Parameter Name Manager Name Manager Type Enabled (control_from_website=1)
False --> True mgractive Pub-80-1 Analysis Tool Manager 1
False --> True mgractive Pub-80-2 Analysis Tool Manager 1
False --> True mgractive Pub-80-3 Analysis Tool Manager 1
False --> True mgractive Pub-80-4 Analysis Tool Manager 1
False --> True mgractive Pub-80-5 Analysis Tool Manager 1
False --> True mgractive Pub-80-6 Analysis Tool Manager 1
False --> True mgractive Pub-80-7 Analysis Tool Manager 1
False --> True mgractive Pub-80-8 Analysis Tool Manager 1
来源：https://stackoverflow.com/questions/58507979/how-to-get-result-set-from-postgresql-stored-procedure