MySQL Blog Posts

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MySQL RDS Point-in-time restore

2016-01-09

RDS for MySQL on AWS allows you to restore to any point in time for your backup retention period, minus the last 5 minutes or so. Restoration creates a new instance, it does not overwrite whatever instance you’re restoring. AWS’s use of the word restore is a bit confusing because restore often means “take your production database server and overwrite it with data from a backup”. As far as I can tell, Amazon never means this. When you restore, AWS creates another database server and writes all the data to the new instance, both when you’re using restoring to a point-in-time or from a DB snapshot. If you needed to switch servers, you’d have to point your database to the new instance.

Reference

Never use floats for money

2014-04-04

UPDATE: Several people have commented that decimal(10,2) is not correct for money, since sometimes currencies go out to more than 2 decimal places. Others claimed that storing cents (or base unit) as integers make it simpler to perform calculations (thanks, Kevin Farley for your comment). Regardless of what you choose – don’t use floats for money. If you do use integers, I would include the base unit in the name to avoid confusion (AmountInCents).

Data types make all the difference in the world when you’re designing your database. The choices you make now will affect the quality of your data, as well as application performance. I’m going to focus on one issue in this article: why you should always use decimals to represent money. Let’s jump in and see why that’s true. Read more

Interviewing for a Database Developer

2014-03-17

I work for a firm that’s heavily invested in SQL – a team that needs to have developers who know their way around relational databases and MySQL in particular. I want to show you how I run interviews for our development positions. Read more

Tiny happy features in MySQL

2014-03-07

I love it when software gives you elegant ways of solving your problem. Programming language designers make me feel like they care when they take the time to include succinct, powerful expressions. I’ve recently discovered some in new things in MySQL, as well as a few rediscoveries. This is the first five, and I’ll cover the next five in another article. Read more

Inner vs. Outer Joins

2014-03-05

join

I want to teach you the difference between an inner and an outer join. We first need to think about what a join is. Simply, it’s when you combine two tables to make a new one. You’re not physically creating a new table when you join them together, but for the purposes of the query, you are creating a new virtual table. Every row now has the columns from both tables. So if TableA has columns Col1 and Col2 and TableB has columns Col3 and Col4, when you join these two tables, you’ll get Col1, Col2, Col3, and Col4. Just as with any query, you have the option of including all columns or excluding some, as well as filtering out rows. Read more


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