Well, that and SQL has a somewhat undeserved reputation for being easy to learn, but also easy to screw up. Like you write a simple looking query and it turns out to have O^2 complexity and your system ends up bogged down in the database forever.
In practice people who fall into complexity traps are usually asking a lot more of their database engine than any beginner. It's usually not that hard to figure out the approximate cost of a particular query.
> Like you write a simple looking query and it turns out to have O^2 complexity
Or you have a simple fast query with a lovely plan until the database engine decides that because you now have 75 records in the middle table instead of 74, the indexes are suddenly made of lava and now you're table-scanning the big tables and your plan looks like an eldritch horror.
In practice people who fall into complexity traps are usually asking a lot more of their database engine than any beginner. It's usually not that hard to figure out the approximate cost of a particular query.