[perrygeo]

Learn SQL (because it's basically the only option) but much more importantly, learn databases. Know why atomicity, consistency, idempotency, and durability matter. Understand the wire protocol and the client-server model. Do relational data modeling; think beyond databases as a dumb store. Join. Know when to normalize. Internalize indexing strategies. Think deeply about what work belongs on the database server (work that can leverage relational set theory) and what work stays in the application. Once you figure the true capabilities of databases, SQL as the language interface is a side note - about as important as the leather on your steering wheel.

[sgarland]

I agree with everything except this:

> Understand the wire protocol and the client-server model.

I'm a DBRE, and have locally compiled MySQL with debug symbols to step through something with gdb. I have yet to examine the wire protocol for MySQL or Postgres beyond a brief read from docs. I'm not saying it's not useful in some circumstances, but I can't think of a reason why a developer would ever need to know it.

[EvanAnderson]

I take "understand the wire protocol" to mean, perhaps, understand nature and shape of the communication between the client and the server.

Here's an "understand the wire protocol" story:

Years ago I dealt with a Customer's thick-client Win32 ERP application that back-ended into Oracle. They wanted to use it across a VPN. They naively thought bandwidth would be the major potential showstoppper and did measurement of bandwidth usage on their own. The app didn't throw around many bits so the Customer declared the test a success and spent the money on the VPN solution.

After the VPN was implemented they were unhappy w/ the performance of the app and asked me to take a look.

The application was built with individual SQL queries "bound" to many of the UI controls. Depending on what the user was doing, displaying a dialog might require 20+ round-trips to the Oracle server. The developers just assumed LAN latency and gave no thought to minimizing round trips.

Web devs are used to dealing with RTT latency today, but this was another time. The devs had no sense of how the wire protocol worked and ended-up making users like my Customer hamstrung into "solutions" like Remote Desktop / VDI.

[sceadu]

the I in ACID stands for isolation, not idempotency