The cursor query and select value
query returns rows if I run it in mysql
but when in a cursor it always exits out of loop.
Anything wrong here?
I've added "BEFORE LOOP", "EXIT" and "IN LOOP" so it prints where it is but it always starts with BEFORE LOOP
and then ends with EXIT
.
CREATE PROCEDURE getTotal()
BEGIN
DECLARE HOSTID INTEGER;
DECLARE cITEMID INT;
declare finished bool default false;
DECLARE Total INT;
declare cur1 cursor for SELECT itemid FROM items WHERE hostid = 10579;
declare continue handler for not found set finished = true;
open cur1;
loop_1: loop
fetch cur1 into cITEMID;
SELECT "BEFORE LOOP";
if finished then
SELECT "EXIT";
leave loop_1;
end if;
SELECT "IN LOOP";
-- Test query
SELECT value from history_uint WHERE itemid = cITEMID ORDER BY itemid DESC LIMIT 1;
-- Final select query will look like this.
-- SET @Total := @Total + (SELECT value from history_uint WHERE itemid = cITEMID ORDER BY itemid DESC LIMIT 1);
-- SELECT @Total;
end loop;
close cur1;
END //
DELIMITER ;
Queries:
SELECT itemid FROM items WHERE hostid = 10579;
| itemid |
| 12345 |
| 12346 |
| 12347 |
SELECT value from history_uint WHERE itemid = 12345 ORDER BY itemid DESC LIMIT 1;
| value |
| 1 |
SELECT * from history_uint;
| itemid | value | clock (unixtimestamp) |
| 12345 | 13 | 4364564654654 |
| 12346 | 1 | 4364564654657 |
| 12347 | 16 | 4364564654654 |
| 12345 | 13 | 4364564654756 |
| 12346 | 2 | 4364564654753 |
| 12347 | 15 | 4364564654756 |
Note: The clock column value is just made up.
Best Answer
Figured out the issue.
Variable should not be the same as any column in the query.
Since the
cur1
query has a column namedhostid
it will trigger thenot found
continue handler which setsfinished
variable totrue
.Not only it triggers continue handler but in some cases it can produce syntax error. Source - https://stackoverflow.com/a/60988686/13109839
Solution rename the
HOSTID
variable to_HOSTID
.