MySQL multiple updates - rollback if one fails - mysql

I need to update multiple rows in multiple tables and in case one of the updates fails, I want to undo all the changes done so far. How can I achieve that? Is a transaction enough?
START TRANSACTION;
UPDATE TABLE1;
UPDATE TABLE2;
UPDATE TABLE3;
COMMIT;


you need to do a rollback on error instead of a commit, e.g. with a handler
DECLARE `_rollback` BOOL DEFAULT 0;
DECLARE CONTINUE HANDLER FOR SQLEXCEPTION SET `_rollback` = 1;
START TRANSACTION;
UPDATE table1;
UPDATE table2;
UPDATE table3;
IF `_rollback` THEN
ROLLBACK;
ELSE
COMMIT;
END IF;

Related

Will errors handled in sub mysql transactions trigger rollbacks in the mysql transaction that calls it

Assume I have a procedure called prodInner that has an error handler like so
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
GET DIAGNOSTICS CONDITION 1
#p1 = RETURNED_SQLSTATE, #p2 = MESSAGE_TEXT;
SELECT #p1 as RETURNED_SQLSTATE, #p2 as MESSAGE_TEXT;
ROLLBACK;
END;
and an outer prod called prodOuter with the same error handler. Say there's an issue when running the inner handler and the sqlexception catches it. Will the outer procedure also "fail" and rollback any and all changes (in addition to changes made in other procedure calls)?
Edit
DROP PROCEDURE TEST_INNER;
CREATE PROCEDURE TEST_INNER()
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
ROLLBACK;
RESIGNAL;
END;
START TRANSACTION;
INSERT INTO TEST_TABLE VALUES (1,0);
INSERT INTO TEST_TABLE VALUES(1); # throws an error because two values are required
COMMIT;
end;
CREATE PROCEDURE TEST_OUTER()
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
ROLLBACK;
RESIGNAL;
END;
START TRANSACTION;
INSERT INTO TEST_TABLE VALUES (-1,0);
CALL TEST_INNER();
COMMIT;
end;
CALL TEST_OUTER()
CALL TEST_INNER()
Edit 2, is this the best solution?

Statements That Cause an Implicit Commit
Transaction-control and locking statements. BEGIN, LOCK TABLES, SET autocommit = 1 (if the value is not already 1), START TRANSACTION, UNLOCK TABLES.
You may investigate this in details: https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=76bc26fa4e96b5ea3643aabe8161feea

I think I've figured out the issue but my understanding is very minimal. When the outer procedure is called, a transaction is created. The commit in the inner-procedure however will commit any and all changes in the inner procedure even if the changes in the inner procedure gets rolled back.

Rolling back a failed SQL query

I am trying to implement a ROLLBACK functionality on my stored procedure that executes 2 UPDATE queries. I want the second update to only run if the first update was successful. Also if the second update fails, there should be a rollback of the first update statement. I did the below but I need to confirm from you guys if what I wrote is okay. Here is my stored procedure
BEGIN
declare exit handler for sqlexception
BEGIN
rollback;
END;
declare exit handler for sqlwarning
BEGIN
rollback;
END;
START transaction;
FIRST UPDATE
SECOND UPDATE
COMMIT;
SELECT FOUND_ROWS() INTO res;
END

commit and rollback for specified cases

can we put a check (sort of) to-
Check if data is committed to database only when the operation is successfully completed.
Data should be rolled back in case of failed transactions.
like this one-
DELIMITER $$
CREATE PROCEDURE `sp_fail`()
BEGIN
DECLARE `_rollback` BOOL DEFAULT 0;
DECLARE CONTINUE HANDLER FOR SQLEXCEPTION SET `_rollback` = 1;
START TRANSACTION;
UPDATE customer SET age= 20 WHERE name='stark';
UPDATE customer SET age= 20 WHERE name='brian'; -- fail as there is no name as brian in the table customer
IF `_rollback` THEN
SELECT 'The transaction has failed' AS 'Result';
ROLLBACK;
ELSE
SELECT 'The transaction was successful' AS 'Result';
COMMIT;
END IF;
END$$
DELIMITER ;
Its mine modified version of one of the answers in stackoverflow itself.I was thinking of using this to solve the above mentioned points but when i call the procedure the call runs successfully but no rows are affected.Why is that ?
Thanks in advance.

There is Autocommit properties in mysql. You will need set AUTOCOMMIT=0 (this set the autocommit false), after that you can issue COMMIT or ROLLBACK at the end of query according to your condition.
1. INSERT INTO table_name ...;
2. COMMIT; -- confirm your changes
OR
3. ROLLBACK; -- undo your changes

How can I use transactions in my MySQL stored procedure?

I'm trying to modify my MySQL stored procedure and make it transactional. The existing stored procedure works fine with no problem but as soon as I make it transactional it does not even allow me to save my changes. I checked MySQL documentation and searched online but I cannot find any problem with my code. It seems to be pretty straight forward but can't figure it out.
BEGIN
DECLARE poid INT;
DECLARE EXIT HANDLER FOR SQLEXCEPTION SQLWARNING
BEGIN
ROLLBACK;
END
START TRANSACTION;
-- ADD option 5
INSERT INTO product_option(product_id,option_id,required) VALUES(insertedProductID,5,0);
SET poid = (SELECT LAST_INSERT_ID());
INSERT INTO product_option_value(product_option_id,product_id,option_id,option_value_id,quantity,subtract,price,price_prefix,points,points_prefix,weight,weight_prefix) VALUES(poid,insertedProductID,5,50,0,0,4.99,'+',0,'+',0,'+');
-- ADD option 12
INSERT INTO product_option(product_id,option_id,required) VALUES(insertedProductID,12,1);
-- ADD option 13
INSERT INTO product_option(product_id,option_id,required) VALUES(insertedProductID,13,0);
COMMIT;
END
any idea ?

Two syntax errors:
You need commas in between the conditions for your exit handler. Notice the syntax documentation shows commas.
You need to terminate the END of the exit handler with a semicolon. The DECLARE statement itself (including its BEGIN...END block) is a statement like any other, and need to have a terminator.
So you need this:
DECLARE EXIT HANDLER FOR SQLEXCEPTION, SQLWARNING
BEGIN
ROLLBACK;
END;

Try like this ie, include your Declare statement inside the START TRANSACTION;. Earlier your ROLLBACK was not a part of TRANSACTION as you wrote it above the START TRANSACTION:-
BEGIN
DECLARE poid INT;
DECLARE EXIT HANDLER FOR SQLEXCEPTION, SQLWARNING
START TRANSACTION;
BEGIN
ROLLBACK;
END
-- ADD option 5
INSERT INTO product_option(product_id,option_id,required) VALUES(insertedProductID,5,0);
SET poid = (SELECT LAST_INSERT_ID());
INSERT INTO product_option_value(product_option_id,product_id,option_id,option_value_id,quantity,subtract,price,price_prefix,points,points_prefix,weight,weight_prefix) VALUES(poid,insertedProductID,5,50,0,0,4.99,'+',0,'+',0,'+');
-- ADD option 12
INSERT INTO product_option(product_id,option_id,required) VALUES(insertedProductID,12,1);
-- ADD option 13
INSERT INTO product_option(product_id,option_id,required) VALUES(insertedProductID,13,0);
COMMIT;
END

Put your DECLAREs after the first BEGIN and it should work.
If you use BEGIN and END to group multiple statements, you normally also need to declare an alternate DELIMITER at the top and replace the ; after the last END with it.

Mysql nested transaction with rollback

Can someone tell me if it is possible to call another procedure from within a procedure and if any part of either procedure fails, roll everything back?
If this is possible, can someone please show me a tiny example of how this would be implemented?
EDIT: Procedure "b" fails but procedure "a" still inserts a row into table "a". It's my understanding that if any part of the insert fails that everything (both inserts) is rolled back which is not happening here. The questions is why not?
Procedure "a"
BEGIN
DECLARE b INT DEFAULT 0;
DECLARE EXIT HANDLER FOR SQLWARNING ROLLBACK;
DECLARE EXIT HANDLER FOR SQLEXCEPTION ROLLBACK;
START TRANSACTION;
INSERT INTO a(a)
VALUES(iA);
CALL b(iB,LAST_INSERT_ID(),#b);
SELECT #b INTO b;
IF b !=1 THEN
ROLLBACK;
ELSE
COMMIT;
END IF;
END
Procedure "b"
BEGIN
DECLARE b INT DEFAULT 0;
DECLARE EXIT HANDLER FOR SQLWARNING ROLLBACK;
DECLARE EXIT HANDLER FOR SQLEXCEPTION ROLLBACK;
START TRANSACTION;
INSERT INTO b VALUES(iB,id);
SET b=1;
COMMIT;
END;

You will need to handle transactions in both procedures, but the proc that is calling the other, should check for the return value and rollback it's transactions based on that. Here is an example of the inner proc:
How to detect a rollback in MySQL stored procedure?
you would then check for p_return_code and do a rollback of the parent transaction.
EDIT:
What I think is happening is that inner SP COMMIT or ROLLBACK affect outer SP TRANSACTION. This code works for me, if inner SP fail it rolls back both insert statements. First call to ab() works, new user record gets inserted and new game record gets inserted, if we remove record from the games table and run ab() again, because user id already exists it rolls back games table insert:
create procedure ab()
BEGIN
START TRANSACTION;
INSERT INTO games (title) VALUES ('bad game');
CALL ba(#ret);
IF #ret!=0 THEN
ROLLBACK;
ELSE
COMMIT;
END IF;
END;
create procedure ba(OUT return_value tinyint unsigned)
BEGIN
DECLARE exit handler for sqlexception
BEGIN
set return_value = 1;
END;
INSERT INTO users (id) VALUES(1);
set return_value = 0;
END;
To test use call ab();