Temporal tables were introduced with SQL Server 2016. To take advantage of this feature, you might start fresh with a brand new table. It is possible, however, to convert an existing table with accumulated history to the new functionality. In this article, Mala Mahadevan explains how to create temporal tables for both scenarios.… Read more
Whether or not to have NULLable columns in a table can be a religious debate, and how missing data is represented should be carefully considered during database design. In this article, Joe Celko considers the ways that SQL Server handles NULLs in several situations. … Read more
SQL naming conventions for tables, and all the associated objects such as indexes, constraints, keys and triggers, are important for teamwork. Poorly-named tables and other objects make it difficult to maintain databases. Table names must follow the rules for SQL Server identifiers, and be less than 128 characters. It is possible to force SQL Server to … Read more
You have many options when exporting data from a database. In this article, Phil Factor compares several methods including XML and array-in-array JSON for speed and file size.… Read more
So you have a database with JSON in it. Can you validate it? I don’t mean just to ensure that it is valid JSON, but ensure that the JSON contains values that are legitimate. Are NI values, postcodes or bank codes valid? Can the dates or GUIDs be successfully parsed? Are those integers really integers? … Read more
JSON was initially designed for the informal transfer of data that has no schema. It has no concept of a table, or of an array of identical arrays. This means that it must tell you each key for each object, even if the original data object was a table. With the happy minimum of key-value … Read more
Now that SQL Server 2019 is on the way, it’s time to start learning about the new capabilities. In this article, Greg Larson tests the new APPROX_COUNT_DISTINCT function for performance and accuracy.… Read more
JSON is a viable option for transferring data between systems. It has the ability to include schema information along with the data which is an advantage over CSV files. In this article, Phil Factor demonstrates how he takes advantage of JSON when exporting or importing tables. … Read more
If you are, as you should be, checking JSON data in a whole lot of files before you import them into your database, you would do well to use JSON Schema, because you can run a number of checks such as regex checks that can’t be done any other way, and it is usually possible … Read more
I am in the middle of working on my DB Design conference that occurs in a bit over a week from now. But I had this come up in some work I was doing and wanted to put it down in a blog. One of the most exciting features of SQL Server 2005 was the … Read more
The other day, I had a problem with some data that I never dreamed I would ever see. In a case insensitive database, in a table’s column that was case insensitive, the customer was using the data as case sensitive. Firstly, let’s just go ahead and say it. “This was a sucky implementation.” But as … Read more
T-SQL window functions, introduced in 2005 with enhancements in 2012, are great additions to the T-SQL language. In this article, Kathi Kellenberger explains what you need to know to get good performance when using these functions.… Read more
Missing data is a difficult and common problem to solve. In this article, Joe Celko explains several approaches to deleting or replacing missing data.… Read more
Assumptions are generally terrible things for programmers (and likely my next “What Counts” blog goes there), because what looks to be true when trying things out on your machine, may not be so at a larger scale. There are lots of examples out there, sorting when there’s a clustered index, not checking errors because you … Read more
T-SQL window functions were introduced in 2005 with more functionality added in 2012. Many database professionals are not aware of these useful functions. In this article, Kathi Kellenberger provides a quick overview of just what a window function is as well as examples of each type of function.… Read more
In-Memory OLTP was introduced with SQL Server 2014 as a way to improve transaction performance. There are several scenarios that are not supported, such as some data types, and Darko Martinović describes the issues and provides workarounds. He also has provided a tool to assist in migrating disk-based tables to In-Memory optimized tables.… Read more
Microsoft introduced native support for JSON in SQL Server in version 2016. In this article, Phil Factor shows how to import JSON documents into to SQL Server database tables, even if there is a bit of complexity in the original data.… Read more
I am a firm advocate of commenting code, but you need to make sure that you are commenting the right thing. I worked on a project last year and then the project was paused. I’m now back on it full time, some 6 months later. I wrote most of the database code and all calls … Read more
In the final article of this series, Robert Sheldon shows how to move from a relational structure to a graph structure using the Graph Database feature.… Read more
The Graph Database feature, new with SQL Server 2017, can be used to represent hierarchies. In this article of the series, Robert Sheldon demonstrates how to represent hierarchies in data with complex relationships.… Read more
Compliant Database DevOps
