… the answer. “Is there a performance difference between putting the JOIN conditions in the ON clause or the WHERE clause in MySQL?” No, there’s….ID = B.ID; SELECT * FROM A JOIN B ON A.ID = B.ID; SELECT * FROM A JOIN B USING(ID); Personally, I prefer to stay away from “comma joins” because a…
Post: JOIN Performance & Charsets
October 21, 2008 By 2 Comments
…. Either way, the character sets used on joined columns can have a significant impact on the performance of your queries. Take the following example… explicit call to CONVERT() in the WHERE clause. This is a result of the joined columns being of different character sets. The….33 to 3.12 seconds. This test was performed with MySQL 5.0.67, FreeBSD 7, on a box with 2GB RAM.
Post: Join performance of MyISAM and Innodb
May 29, 2006 By 6 Comments
…, having with about 20.000 rows in it on 32bit Linux. The columns “id” “i” and “c” …it does not return many rows. I varied the join clause to be id, i and C columns appropriately. …MyISAM does compression for character keys which makes it perform slower for random lookups MyISAM generally has lower …
Post: How adding another table to JOIN can improve performance ?
August 1, 2008 By 12 Comments
JOINs are expensive and it most typical the fewer tables (for the same database) you join the better performance you will get. As… table in join is estimated same in original query) and we get the range clause on “info” table instead nested loops join – exactly what… as the query using join with day list table. So we finally managed to get better performance by joining data to yet another…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 12 Comments
…is specified as the first argument on the command line: $ cat sales….join/where. You may not use sub-queries or any non-deterministic functions like NOW() or RAND(). HAVING clauses, ORDER BY clauses… difference in response time. Refresh method performance comparison For demonstration purposes, I did …
Comment: Is there a performance difference between JOIN and WHERE?
November 5, 2011 By 25 Comments
… three ways to do this, but which one would be performing best considering the first table to be huge (100 thousands…) join, id of table to be updated in ON clause, the other id in where clause UPDATE table_1 a INNER JOIN table_2 b ON… WHERE a.id = 3) join, both ids in ON clause UPDATE table_1 a INNER JOIN table_2 b ON a.id = AND b.id…
Comment: Is there a performance difference between JOIN and WHERE?
November 5, 2011 By 25 Comments
… three ways to do this, but which one would be performing best considering the first table to be huge (100 thousands…) no join, and both ids in where clause as stated above 2) join, one id in ON clause, the other id in where clause UPDATE table_1 a INNER JOIN table_2 b ON…
Post: Derived Tables and Views Performance
August 31, 2006 By 14 Comments
… each other but how do they compare in terms of performance ? Derived Tables in MySQL 5.0 seems to have different… mistake in select in from clause, ie forgotten join condition you might have EXPLAIN running forever. Views on other hand do not have… view creator. What does it mean in terms of performance: Query on base table executes using index and it is very fast…
Post: The MySQL optimizer, the OS cache, and sequential versus random I/O
April 28, 2008 By 17 Comments
In my post on estimating query completion time, I wrote about how I measured the performance on a join between a few tables in… dimension columns are indexed on every table, and there’s a separate index on every column in the WHERE clause. Here’s the… for days? Here’s my train of thought: It’s performing index lookups into the fact table, which is big. An…
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 93 Comments
…on most selective columns would be good idea for performance of such queries. For example you may put index on…for, if you do not have full where clause resolved by index is how many rows you…or “system” access type it is effectively removed from join execution (replaced with constants) and so ORDER …
