使用开始事务设置var mysql

Question

i don't familiar at database, That is my test syntax:

START TRANSACTION ;
SET @VAR = (SELECT `some ID` FROM `some table` ORDER BY `some ID` DESC LIMIT 1);
SELECT @VAR;
COMMIT;
SELECT @VAR;

i think is result is first select is null (because before commit) and second select is have value, and in my test first and second select have value, why? and how to fix my syntax?

Answer 1

You seem confused. First, changes made within a transaction are visible within the same transaction. Second, transactions are about changes to the database , not changes to the session . After all, the database is ACID-compliant (or not), not the variables in a session.

The first print prints the value present during the transaction. Changes within a transaction are visible -- in the transaction. This is true for changes on tables, as well. If you insert a row in a table and -- in the same transaction -- look for the row, then you will see it.

You should not see the row in another session. You won't see it elsewhere, until the changes are committed.