table-locking

I have two innodb tables: articles id | title | sum_votes ------------------------------ 1 | art 1 | 5 2 | art 2 | 8 3 | art 3 | 35 votes id | article_id | vote ------------------------------ 1 | 1 | 1 2 | 1 | 2 3 | 1 | 2 4 | 2 | 10 5 | 2 | -2 6 | 3 | 10 7 | 3 | 15 8 | 3 | 12 9 | 3 | -2 When a new record is inserted into the votes table, I want to update the sum_votes field in articles table by calculating the sum of all votes. The question Which way is more efficient, if the SUM() calculation itself is a very heavy one ( votes table has 700K records). 1. Creating a trigger CREATE TRIGGER

This was my original question: I am trying to figure out how to enforce EXCLUSIVE table locks in SQL Server. I need to work around uncooperative readers (beyond my control, closed source stuff) which explicitly set their ISOLATION LEVEL to READ UNCOMMITTED. The effect is that no matter how many locks and what kind of isolation I specify while doing an insert/update, a client just needs to set the right isolation and is back to reading my garbage-in-progress. The answer turned out to be quite simple - while there is no way to trigger an explicit lock, any DDL change triggers the lock I was

I need to create an index on a ~5M rows MySQL table. It is a production table, and I fear a complete block of everything if I run a CREATE INDEX statement... Is there a way to create that index without blocking inserts and selects? Just wondering I have not to stop, create index and restart my system! [2017] Update: MySQL 5.6 has support for online index updates https://dev.mysql.com/doc/refman/5.6/en/innodb-create-index-overview.html In MySQL 5.6 and higher, the table remains available for read and write operations while the index is being created or dropped. The CREATE INDEX or DROP INDEX