I tried to write a recursive function, which is not possible. (I'm trying to check if a given row has a given ancestor somewhere in its chain). So, i wrote this check as a procedure instead. But I can't call a procedure within a select statement.
What's the solution for such a case?
i found a solution.
it's possible to use a function which internally calls a procedure
Related
I'm using mysql and I want to use the if statement in a way you are doing in a stored procedure. Something like this:
delimiter $$
if #myVariable is null then
drop temporary table tmp_buffer;
select 'cannot proceed without variable #myVariable';
else
update my_table as t
set t.name = #myVariable;
end;
end$$
delimiter ;
When I execute this code it does nothing.
I tried to google this but I only find select if(....) explanations what doesn’t fit to my requirements.
I know that it is possible to create a stored procedure and put the code there and then call the procedure, but I'm looking for a way to do it without stored procedures.
Is this possible? If yes, what is wrong in my code?
Thanks for reading this
Felix
but I'm looking for a way to do it without stored procedures. Is this
possible?
NO; as already commented above, you cann't use if .. else construct block like the way you are intend to use in a normal SQL query. You will have to wrap it inside a procedural block which could be a stored procedure or a function.
I have MySQL procedure where I want to get a result of query:
SELECT id FROM mbus_clients WHERE second_name like surnamePart AS
So it should be an array. The decision I've found in the internet is to use temporary table.
But how can I return a table and read with PHP? Is it ok?
Simply call the procedure:
CALL procedurename();
If the procedure performs a SELECT, the result set of the procedure call will be the same as if you'd performed the query itself. You can then fetch the rows using PHP the same way as if you'd performed a SELECT.
I have execute only access to a stored procedure.
This SP seems to select some data from multiple tables, and returns one row. I need to store two columns of the output of this SP into a table.
Is there any way to do this within MySQL?
If it returns a row, this is a stored function and not a stored procedure. You can use something like the following to insert into your table:
INSERT INTO tablename SELECT (SELECT col1, col2 FROM (SELECT somefunction()))
Otherwise, it will be a stored procedure and you should do something like this, assuming that #var1 and #var2 are output parameters:
CALL someprocedure(#var1, #var2, #var3)
INSERT INTO tablename SELECT(#var1, #var2)
See the documentation about Create Procedure and Create Function for more information about functions versus procedures.
MySQL has an extension to stored procedures that allows the procedure to return one or more result sets to the client, as if the client had issued a SELECT query... but those results are ephemeral. They don't persist and they can't be stored in variables or otherwise accessed after the procedure finishes -- they can only be "fetched" the one time.
There is a way to make them accessible without breaking the way the procedure already works, as I discussed here, but you can't do it without a change to the procedure:
How to use Table output from stored MYSQL Procedure
The idea is for the procedure to write its output in a temporary table, and then return it to the caller by calling SELECT against the temporary table -- but to leave the temporary table behind so that the caller can access it directly if desired.
That's not exactly the same as what you're asking though, which is why I didn't mark this question as a duplicate, since you, unlike the other poster, do not appear to have administrative control of the procedure... but unless you can make the case for a change like this, there's not another way within MySQL to access those returned values, since they only exist in the result-set that's returned.
Of course, procedures do have optional OUT parameters, where you can hand variables to the procedure as part of arguments you use to call it, and it can set those variables, so that they'll have the values you need when the procedure is done, but that only works when the return values are scalars and would require a change to the procedure's interface, since procs in MySQL do not have "optional" arguments... if the procedure were changed to permit this, it would require an increased number of arguments to be provided every time it was called, and if other components are calling it, that could easily break other things.
I have a procedure that creates a table, is it possible to have a view (or similar) that can call the procedure then select from the table?
I've tried this:
DELIMITER $$
CREATE DEFINER=`root`#`localhost` FUNCTION `new_routine`(p1 INT) RETURNS int(1)
BEGIN
CALL rMergeDateFields();
RETURN 1;
END
CREATE VIEW `db`.`vIntervals` AS
SELECT new_routine(0) AS col1;
SELECT * FROM MergedData;
but I get this error
Error 1422: Explicit or implicit commit is not allowed in stored function or trigger.
Any ideas?
No, you cannot. Views are typically read-only operations; and that behavior cannot be guaranteed if stored-procedures are invoked.
Related question:
How to call Stored Procedure in a View?
Is it possible to call stored procedure in view?
Here is a canonical resource:
http://dev.mysql.com/doc/refman/5.1/en/view-updatability.html
Some views are updatable. That is, you can use them in statements such as UPDATE, DELETE, or INSERT to update the contents of the underlying table. For a view to be updatable, there must be a one-to-one relationship between the rows in the view and the rows in the underlying table. There are also certain other constructs that make a view nonupdatable.
As invoking the stored procedure cannot assure 1:1 relationships with view rows, the update is not permitted.
You can't do this from a view, but a stored procedure itself can return a result set.
DELIMITER $$
CREATE DEFINER=`root`#`localhost` PROCEDURE `merge_and_select` ()
BEGIN
CALL rMergeDateFields();
SELECT * FROM MergeData;
END $$
If you CALL merge_and_select() the rMergeDateFields procedure will be run and then you will get the contents of the MergeData table returned to you, in one step... which sounds like what you're wanting.
This is, however, a really bad implementation, because there's no control for concurrent calls to merge_and_select(), so all kinds of things could go wrong if it's run more than once at the same time.
However, depending on what you really need rMergeDateFields() to do, it's possible that you could rewrite rMergeDateFields() to actually perform whatever work you need done and return it directly to the client without using the MergeData table using an unbounded SELECT, as shown above.
Anything you SELECT in a stored procedure without using INTO a variable is returned to the client as a response from the CALL.
I need to make a stored procedure or function that returns a set of rows. I've noted that in a stored procedure i can SELECT * FROM table with success. If i fetch rows in a loop and SELECT something, something_other FROM table once per loop execution, I only get one single result.
What I need to do is looping, doing some calculations and returning a rowset. What's the best way to do this? A temporary table? Stored functions?
Any help appreciated.
It sounds like you're using a cursor inside the body of the stored procedure to accomplish your looping?
My first advise is: try to do your calculations in a single query without resorting to cursors. What's the calculation exactly?
If you really do need to use a cursor, then INSERT the results of each loop into a temporary table and then SELECT * from that table when you're done looping.
You can return multiple result sets but only if the client library supports it and the client is expecting it. Some don't, so using them will result in out-of-sequence errors.
You can certainly build a temporary table, select from it and drop it inside the procedure, that would be safe. Another option is to build a UNION select using a prepared SQL statement which returns all the rows you need and execute that. That's a bit messy.