SQL Server concepts – Page 3

Operations that need a serial plan

Some operations in SQL Server will turn your entire query plan serial (single-threaded), others will just reserve a so-called “serial zone”. I read up on this stuff a number of years ago (including a great post by Paul White), and thinking that some things must have changed since, I decided to go see for myself.

Quiz: What’s going on here, then?

I’m trying a new type of blog post, and if it works out, I would be happy to post more of the same going forward. The format is a real-world troubleshooting mystery, and I’ll clue you in to the details along the way.

How quickly can you crack it?

Computed columns with scalar functions

Scalar functions can be a real headache when you’re performance tuning. For one, they don’t parallelize. In fact, if you use a scalar function in a computed column, it will prevent any query that uses that table from going parallel – even if you don’t reference that column at all!

Legacy apps that don’t believe in schemas

Inspired by an actual customer scenario: what if you have a legacy app that doesn’t schema-prefix its database objects, but you want it to work with a specific assigned schema? There’s a quick and easy solution.

Effective permissions on SQL Server

SQL Server Management Studio allows you to view effective permissions on an object, but it’s limited in a few important respects. To work around some of those limitations, I’ve built a stored procedure to display all the defined and effective permissions across an entire SQL Server database.

Automatically guessing foreign key constraints

With good naming and datatyping conventions, an automated script can help you with the process of creating foreign key constraints across your database, or actually, suggest table relations where you’ve forgotten to implement them.

Practical uses of binary types

The binary datatype of SQL Server is one of those features most developers don’t really use that often, but it turns out there’s more to binary values than just storing large, non-relational blobs.

A visual representation of SQL Server Agent jobs

If all you have is a hammer, everything will eventually start looking like a nail. This is generally known as Maslow’s hammer and refers to the fact that you use the tools you know to solve any problem, regardless if that’s what the problem actually needs. With that said, I frequently need a way to visualize the load distribution of scheduled jobs over a day or week, but I could never be bothered to set up a web server, learn a procedural programming language or build custom visualizations in PowerBI.

So here’s how to do that without leaving Management Studio.

Availability Groups: How to sync logins between replicas

AlwaysOn Availability Groups are a reasonably simple way to set up disaster recovery (DR) for your SQL Server environment, and with fairly little effort, you can get a bit of high availability (HA) from it as well. But there are a few gotchas, the most obvious of them being that Availability Groups only synchronize specific user-databases, not the entire server setup.

Things that are not included in AGs include logins, SQL Server Agent jobs, SSIS packages stored in SQL Server, linked servers and server settings. You could sync these manually (as is often the case), but wouldn’t you just love to have an automated process do all this for you?

In this post, we’ll look at logins. For the sake of simplicity, I’ll assume that you have a primary replica with a single AG and any number of secondary replicas. The logic holds true if you have multiple AGs, it just gets trickier.

Video: three SQL Server join operators in three minutes

In an attempt to try a different approach, here’s a three-minute video explanation of how the different physical join operators in SQL Server work and why you would choose one over the other.

Category: SQL Server concepts