I try to use subquery in mysql custom user-defined function I get an error so could u help me with one example.
Here is my code:
CREATE DEFINER=`root`#`localhost` FUNCTION `findsubName`(counts INT)
RETURNS varchar(255) CHARSET utf8
BEGIN
DECLARE result VARCHAR(500) DEFAULT NULL;
DECLARE v_name VARCHAR(200);
DECLARE finished INT(1) DEFAULT 0;
DECLARE my_cursor CURSOR FOR
SELECT id, (SELECT t_name FROM ajctb_titles b WHERE a.jt_id=b.t_id)
as tableName FROM ajctb_vacancies a limit counts;
DECLARE CONTINUE HANDLER
FOR NOT FOUND
SET finished = 1;
OPEN my_cursor;
calc_change: LOOP
FETCH my_cursor INTO v_name;
IF finished THEN
LEAVE calc_change;
END IF;
IF result<>'' THEN
SET result = CONCAT_WS(',',result,v_name);
ELSE
SET result = v_name;
END IF;
END LOOP calc_change;
CLOSE my_cursor;
RETURN result;
END
Error message:
Error Code: 1328. Incorrect number of FETCH variables
Error message: Error Code: 1328. Incorrect number of FETCH variables
Error messages attempt to tell you what the problem is. It is in the FETCH. Looking at the documentation:
13.6.6.3 Cursor FETCH Syntax
FETCH [[NEXT] FROM] cursor_name INTO var_name [, var_name] ...
This statement fetches the next row for the
SELECT statement associated with the specified cursor (which must be
open), and advances the cursor pointer. If a row exists, the fetched
columns are stored in the named variables. The number of columns
retrieved by the SELECT statement must match the number of output
variables specified in the FETCH statement.
https://dev.mysql.com/doc/refman/8.0/en/fetch.html
2 columns in your query:
SELECT
id
, (
SELECT
t_name
FROM ajctb_titles b
WHERE a.jt_id = b.t_id
)
AS tableName
means 2 variables are needed the FETCH
It hasn't even attempted the subquery yet.
Regarding that correlated subquery it could be a problem. When you use a subquery in the select clause like this it MUST return no more then one value. So you should use limit 1 if you continue with that subquery.
That subquery can be replaced with a join. e.g.
SELECT
id
, b.t_name AS tableName
FROM ajctb_vacancies a
LEFT JOIN ajctb_titles b ON a.jt_id = b.t_id
You may want to use an INNER JOIN if you must always have a non-null tablename returned.
Related
I'm trying to implement a cursor in MYSQL. Inside that cursor, I have a select statement that might or might not return any rows.
I'm facing a problem when that query does not return any rows.
According to the MYSQL documentation,
NOT FOUND: Shorthand for the class of SQLSTATE values that begin with '02'. This is relevant within the context of cursors and is used to control what happens when a cursor reaches the end of a data set. If no more rows are available, a No Data condition occurs with SQLSTATE value '02000'. You can set up a handler for it or a NOT-FOUND condition to detect this condition. For another example, see Section 13.6.6, “Cursors”. The NOT FOUND condition also occurs for SELECT ... INTO var_list statements that retrieve no rows.
My termination of the cursor is implemented as usual.
DECLARE CONTINUE HANDLER
FOR NOT FOUND SET FINISHED = 1;
The problem is that the termination is triggered because of the query inside the cursor returning 0 rows. Is there a way to differentiate between those two cases so that the cursor continues despite my query returning 0 results?
Thanks in advance.
DROP PROCEDURE IF EXISTS CURSOR_PLACEHOLDER;
DELIMITER $$
CREATE PROCEDURE CURSOR_PLACEHOLDER()
BEGIN
DECLARE FINISHED INTEGER DEFAULT 0;
DECLARE CURRENT_ROW_ID VARCHAR(256);
DEClARE CURRENT_ROW
CURSOR FOR
SELECT ID
FROM A
WHERE ID_P IN (SELECT ID_P
FROM A
GROUP BY ID_P
HAVING COUNT(ID_P) > 1);
DECLARE CONTINUE HANDLER
FOR NOT FOUND SET FINISHED = 1;
OPEN CURRENT_ROW;
GET_ACTION:
LOOP
FETCH CURRENT_ROW INTO CURRENT_ROW_ID;
IF FINISHED = 1 THEN
LEAVE GET_ACTION;
END IF;
SET #CURRENT_P_ID := (SELECT ID_P FROM A WHERE ID = CURRENT_ROW_ID);
SELECT a.ID_U, a.ID_R, a.A, a.FROMDATE, a.TODATE
INTO #ID_U, #ID_R, #A, #FROM_DATE, #TO_DATE
FROM ASSIG a
WHERE a.ID_G = #CURRENT_P_ID; # <- Query that returns 0 rows and terminates the cursor
IF (#ID_U IS NOT NULL) THEN
SET #ASSIG_ID := GENERATE_ID();
INSERT INTO ASSIG
VALUES (#ASSIG_ID,
#G_ID,
#ID_U,
#ID_R,
#A,
#FROM_DATE,
#TO_DATE);
END IF;
UPDATE A
SET ID_P = #G_ID
WHERE ID = CURRENT_ROW_ID;
END LOOP GET_ACTION;
CLOSE CURRENT_ROW;
END
$$
DELIMITER ;
I need to update a table based on the result of a subquery that brings more than 1 value, but with the query below I get the error return "Subquery returns more than 1 row". I would like to know if it is possible to make a "loop" to update the values with each result presented in my subquery below.
Complete Query
UPDATE estoque_tamanhos tam
SET tam.qtde = tam.qtde - IF(NEW.tipo = 'K', NEW.qtde_prod * NEW.qtde_lote, NEW.qtde_prod)
WHERE tam.estoques_id = (SELECT estoques_id
FROM combo_estoque
WHERE produtos_id = NEW.produtos_id)
AND UPPER(tam.tamanho) = UPPER(NEW.tamanho_prod);
Subquery that returns 2 or more values.
SELECT estoques_id FROM combo_estoque WHERE produtos_id = NEW.produtos_id
Result
produtos_id
estoques_id
246
54
246
207
In the ideal scenario, my query would execute the first value, after the second ... third ... without repeating the previous ones.
You should create a stored procedure using Cursors to iterate each result of your query.
CREATE PROCEDURE UPDATING_ROWS(PRODUTO_ID INT, qtde_prod INT, qtde_lote INT, TIPO INT)
BEGIN
DECLARE done INT DEFAULT FALSE;
DECLARE estoque_;
DECLARE cursor FOR SELECT estoques_id FROM combo_estoque WHERE produtos_id = NEW.produtos_id) AND UPPER(tam.tamanho) = UPPER(NEW.tamanho_prod)
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
OPEN cur1;
read_loop: LOOP
FETCH cur1 INTO estoque_;
IF done THEN
LEAVE read_loop;
END IF;
UPDATE estoque_tamanhos tam SET tam.qtde = tam.qtde - IF(TIPO = 'K',
qtde_prod * qtde_lote, qtde_prod)
WHERE tam.estoques_id = estoque_;
END LOOP;
END
You have to create a stored procedure like this to iterate each result of your select query. You can read more about this in this link
I searched a lot of doing a task but found no appropriate solution.
Basically the scenario is. I have a user_comment table in which there are 5 column(id,parent_id,user_comments,is_deleted,modified_datetime). There is a parent child relationship like 1->2,1->3,2->4,2->5,5->7 etc. Now i am sending the id from the front end and i want to update the column is_deleted to 1 and modified_datetime on all the records on
this id as well as the all the children and children's of children.
I am trying to doing this by using a recursive procedure. Below is the code of my procedure
CREATE DEFINER=`root`#`localhost` PROCEDURE `user_comments`(
IN mode varchar(45),
IN comment_id int,
)
BEGIN
DECLARE p_id INT DEFAULT NULL ;
if(mode = 'delete')
then
update user_comment set is_deleted = 1, modified_datetime = now()
where id = comment_id ;
select id from user_comment where parent_id = comment_id into p_id ;
if p_id is not null
then
SET ##GLOBAL.max_sp_recursion_depth = 255;
SET ##session.max_sp_recursion_depth = 255;
call user_comments('delete', p_id);
end if;
end if;
END
By using this procedure it give me an error of more than one row.
If i return the select query without giving it to variable then shows me the the appropriate results on the select query but i have to call this procedure recursively based on getting the ids of the select query.
I need help i have already passed 2 days into this.
I used cursor also. Below is the code of cursor
CREATE DEFINER=`root`#`localhost` PROCEDURE `user_comments`(
IN mode varchar(45),
IN comment_id int,
)
BEGIN
DECLARE p_emp int;
DECLARE noMoreRow INT;
DECLARE cur_emp CURSOR FOR select id from user_comment where parent_id = comment_id ;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET noMoreRow = 0;
if(mode = 'delete')
then
OPEN cur_emp;
LOOPROWS: LOOP
IF noMoreRow = 0 THEN
update user_comment set is_deleted = 1, modified_datetime = now() where id = comment_id
CLOSE cur_emp;
LEAVE LOOPROWS;
END IF;
FETCH cur_emp INTO p_emp;
update user_comment set is_deleted = 1, modified_datetime = now() where id = p_emp ;
SET ##GLOBAL.max_sp_recursion_depth = 255;
SET ##session.max_sp_recursion_depth = 255;
call user_comments('delete', p_emp);
END LOOP;
end if;
END
After using cursor i am getting a thread error.i don't know how can overcome this problem!!!
Mysql's documentation on select ... into varlist clearly says:
The selected values are assigned to the variables. The number of
variables must match the number of columns. The query should return a
single row. If the query returns no rows, a warning with error code
1329 occurs (No data), and the variable values remain unchanged. If
the query returns multiple rows, error 1172 occurs (Result consisted
of more than one row). If it is possible that the statement may
retrieve multiple rows, you can use LIMIT 1 to limit the result set to
a single row.
Since you wrote in the OP that a comment can be parent of many comments, using simple variables cannot be a solution. You should use a CURSOR instead, that can store an entire resultset.
You loop through the records within the cursos as shown in the sample code in the above link and call user_comments() in a recursive way.
UPDATE
If your receive
Error Code: 1436. Thread stack overrun
error, then you can do 2 things:
Increase the thread_stack setting in the config file and restart mysql server.
You can try to simplify your code to use less recursions and therefore less stack space. For example, when you fetch all children into the cursor, then rather calling the user_comments() recursively for each, you can set all direct children's status within the code and call the function recirsively on grand-childrens only (if any). You can also change your data structure and use nested set model to approach hierarchical structures.
Nested set model is more complex to understand, it is less resource intensive to traverse, but more resource intensive to maintain.
I am writing a MySQL Stored Procedure for the first time, and I am running into an issue - I think with the Handler Code. Basically, I want this code to update all rows in the pps_users table, but for some reason I am hitting the 'finished condition' for the handler after only two rows are fetched.
I tried the same thing with the REPEAT syntax and got the same result. If I just run the cursor query I correctly get the 10,000 records I expect, but when I run the whole thing as is, I hit the finished code after only 1 or 2 records.
DELIMITER $$
CREATE DEFINER=`root`#`localhost` PROCEDURE `changeNFLFavTeams`()
BEGIN
DECLARE favNFLTeam varchar(100) DEFAULT "";
DECLARE favNCAATeam varchar(100) DEFAULT "";
DECLARE v_finished INTEGER DEFAULT 0;
DECLARE user_id bigint(20);
DECLARE fullNameOfTeam varchar(100) DEFAULT "";
DECLARE update_favs CURSOR FOR select id, favorite_nfl_team from pps_users WHERE favorite_nfl_team is not null;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_finished = 1;
OPEN update_favs;
updaterecord: LOOP
FETCH update_favs INTO user_id, favNFLTeam;
select user_id, favNFLTeam as "Test";
if v_finished = 1
then
select "finished" as "finished";
LEAVE updaterecord;
end if;
select full_name into fullNameOfTeam
from teams t
inner join display_names dt on dt.entity_id = t.id
and dt.entity_type = 'teams'
and dt.first_name = favNFLTeam
and team_key like 'l.nfl.com%' LIMIT 1;
select user_id, fullNameOfTeam AS "BeforeUpdate";
IF fullNameOfTeam != ''
THEN
-- here for whatever_transformation_may_be_desired
-- Find the Full name for the record they chose
UPDATE pps_users p
SET favorite_nfl_team = fullNameOfTeam
WHERE user_id = p.id;
ELSE
SELECT 'A' AS 'A'; -- no op
END IF;
end loop updaterecord;
CLOSE update_favs;
END
This is because if your SELECT full_name into fullNameOfTeam... query returns no rows, then it will set v_finished to 1. That, apparently, happens early on, and forces an exit from the main loop.
The key is to realize that the CONTINUE HANDLER for NOT FOUND does not apply to the cursor alone.
You should either put the secondary query into its own BEGIN..END block with its own CONTINUE handler, or (easier) just set v_finished = 0 after the SELECT full_name into fullNameOfTeam... statement.
I try to do this
CREATE FUNCTION getOneCentOrderIds (s text) RETURNS text
BEGIN
DECLARE no_more_orders, ent_id INT default 0;
DECLARE ids text;
DECLARE orders_cur CURSOR FOR SELECT entity_id FROM sales_flat_order WHERE total_due = 0.01;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_orders = 1;
OPEN orders_cur;
FETCH NEXT FROM orders_cur INTO ent_id;
REPEAT
SET ids = CONCAT(ids, ', ', ent_id);
FETCH orders_cur INTO ent_id;
UNTIL no_more_orders END REPEAT;
CLOSE orders_cur;
RETURN ids;
END$
but I get null when I execute the function.
If I simply remove concat and leave SET ids = ent_id I get the last id in cursor, as expected.
How should I do the concatenation ?
The concat() function returns NULL if any of its arguments are NULL. Try
DECLARE ids text DEFAULT '';
which will make sure the first call to CONCAT has no NULL arguments.
Instead of creating a function, the above can simple be done in a query as
SELECT group_concat(entity_id) FROM sales_flat_order WHERE total_due = 0.01;