t-sql

Generating Test Data Quickly with the VALUES Clause in SQL Server

by

When you need to test queries, stored procedures, or reporting logic, having quick access to realistic data is imperative. While tools like INSERT...SELECT from other tables or importing CSV files are common, sometimes you just want to spin up a set of rows on the fly without messing with permanent tables. That’s where the VALUES clause can help.

The VALUES clause is usually seen in simple INSERT statements, but it can also be used directly in a SELECT statement to create inline datasets. This can be especially handy for mocking up scenarios, testing joins, or building quick prototypes.

Read more

Handling International Date Formats When Casting to DATETIME in SQL Server

by

Working with dates in SQL Server is usually quite straightforward. There’s a good range of date types and functions that we can use to manipulate date/time values.

But international date formats can undo all that simplicity in a heartbeat. Something as simple as casting a string into a DATETIME type can blow up depending on how the server interprets the input. This often happens when you’re dealing with applications or imports that don’t stick to a single culture or regional setting.

Let’s walk through an example and see why SQL Server behaves this way, and more importantly, how to handle it correctly.

Read more

Using AVG() with DISTINCT in SQL Server

by

When working with averages in SQL Server, it’s easy to assume that AVG() just takes all rows into account and calculates a simple mean. And that’s true. By default, AVG() includes every value in the column you point it to. But sometimes, you may want to average only unique values in that column, which is where DISTINCT comes into play.

Let’s explore this with a simple example.

Read more

Why You Should Consider More than Expected Maximum Values When Choosing SQL Server Column Datatypes

by

When designing a SQL Server database, one of the first tasks is deciding what datatype to use for each column. A common rule of thumb is to choose a datatype that fits the largest value you expect to store. For example, if you know an INT will comfortably hold all expe1cted order quantities, then it seems like a safe choice.

But that logic can fall short in some cases. It completely ignores an important consideration – aggregate queries.

Read more

How to Identify Dependencies Before Dropping a Column in SQL Server

by

Dropping or modifying a column in SQL Server can look straightforward, but it often isn’t. That column might be referenced by other objects in the database, and removing it without checking can break things silently. Unlike dropping a whole table, where SQL Server is very strict about dependencies, column-level references are not always enforced or even tracked. That’s why it’s important to do some homework before making the change.

Read more

Finding Foreign Keys that Use SET NULL for Deletes and Updates in SQL Server

by

When you set up foreign key relationships in SQL Server, you have a choice for how changes in the parent table affect related rows in the child table. One option is SET NULL, which replaces the foreign key value with NULL whenever the parent row is deleted or updated.

This behavior is useful in scenarios where you’d rather keep the child record around but cut the link once the parent no longer exists. For example, if a project is deleted, you might want to keep related tasks but mark their ProjectId as NULL.

The problem is that it’s not always obvious which foreign keys are configured with SET NULL, especially in large databases. Fortunately, SQL Server’s system views make it possible to query this information directly.

Read more

Formatting Numbers for International Users in SQL Server (Locale-Aware)

by

When working with applications that serve people across different countries, you quickly realize that numbers aren’t always written the same way. A salary of 55,000.75 in the U.S. might be displayed as 55.000,75 in Germany or 55 000,75 in France. The decimal and thousands separators change depending on a user’s locale.

If you’re storing numbers in SQL Server but want to display them in a format that makes sense internationally, you’ll want to tap into SQL Server’s locale-aware formatting.

Read more

Comparing COL_LENGTH() and DATALENGTH() in SQL Server

by

SQL Server has a COL_LENGTH() function and a DATALENGTH() function that could easily be confused for doing the same thing. They both have “length” in their name, and they do indeed return a “length”. But the length returned is different for each function.

If you’ve ever wondered why DATALENGTH() gives you different numbers than COL_LENGTH(), read on to find out.

Read more

Simple CONCAT() Usage vs Manual String Building in SQL Server

by

When working with SQL Server, string concatenation is one of those everyday tasks that’s easy to take for granted. It can feel like second nature to reach for the trusty old + operator to piece together strings, but SQL Server also provides an alternative way to handle concatenations. Yes, I’m referring to the CONCAT() function.

And there’s a subtle difference between the two approaches that might sway you towards using one or the other.

Let’s compare these two approaches to building strings in SQL Server.

Read more

Step by Step Guide to Calculating and Formatting Percentages in SQL Server

by

When you’re writing reports in SQL Server, one of the first little annoyances you’ll probably bump into is how percentages show up. By default, SQL Server doesn’t have a built-in “percent” data type. Percentages are usually stored as decimals (for example, 0.25 for 25%), and if you just throw those into a report, they won’t look the way people expect.

So you’ll need to do a bit of work to get it nicely formatted into a percentage format that people expect to see.

Also, if you’re calculating percentages from raw values then that will require some more work.

In this article we’ll walk through an example of how to calculate and format percentages in SQL Server.

Read more