Latest Content

2019-05-17 23:06 UTC

Fun MySQL fact of the day: loose scan semi-join

Yesterday, we considered MySQL's FirstMatch semi-join optimisation, and while it's pretty simple and fairly straight-forward, some queries may just not benefit from it. ... read more

2019-05-16 23:45 UTC

Fun MySQL fact of the day: first match optimisation

If we consider back to Tuesday, one of MySQL's guarantees about subqueries is that it will not return the same row in the outer query twice. Compare this to a join, which will return a copy of the left-hand-table's row for each matching right-hand-table row. ... read more

2019-05-15 23:35 UTC

Fun MySQL fact of the day: subquery materialization

Yesterday, we started looking at the semi-join strategies MySQL provides, and today, we're going to continue looking into semi-joins by considering the "materialisation" strategy. ... read more

2019-05-14 23:30 UTC

Fun MySQL fact of the day: table pullouts

As noted yesterday, MySQL 5.6 was released with a large number of optimisations to the subquery engine. In particular, a number of changes were made to optimise for non-scalar, uncorrelated subqueries, allowing them to be run as... you guess it! Joins. ... read more

2019-05-13 23:05 UTC

Fun MySQL fact of the day: subqueries in MySQL5.5

The year 2013 can be remembered by 3 separate things: Justin Timberlake, the series finale of Breaking Bad, and the release of MySQL 5.6. Though, if you aren't a MySQL historian, the release of MySQL 5.6 may have passed you by and you may have missed the ... read more

2019-05-10 08:00 UTC

Fun MySQL fact of the day: batched key access

We took a small detour from discussing table joins yesterday to take a look at Disk-Sweep Multi-Range Read Optimisation (MRR). If you're wondering why, it's was so that we have a better understanding of how the third of the 3 join algorithms MySQL can use to join tables ... read more

2019-05-09 08:00 UTC

Fun MySQL fact of the day: multi-range read optimisation

So far this week, we've looked at 2 of the 3 Nested-Loop Join algorithms MySQL can use to join tables. Before we look at the third one, we need to take a quick detour. ... read more

2019-05-08 08:00 UTC

Fun MySQL fact of the day: block nested-loop joins

Yesterday, we introduced MySQL's Nested-Loop Join algorithm, which it uses to join tables. In many cases, this is a fairly simple and powerful implementation, but as you may appreciate, sometimes this simplicity may end up being rather inefficient. ... read more

2019-05-07 08:00 UTC

Fun MySQL fact of the day: everything is a nested-loop join

Yesterday, we discussed that all queries in MySQL are joins, including single-table queries, but today, we'll start to focus on multi-table joins. ... read more

2019-05-06 21:23 UTC

Fun MySQL fact of the day: everything is a join

This week, we're going to start looking at table joins in MySQL, which, interestingly enough, is the only way MySQL executes queries. ... read more

1 2 3 4 5 6 7 8 9 Next »