SQL Server

EF Core – Database schema changes

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Anytime you change the definition of the database – from renaming a column to creating a table – it’s referred to as a database schema change. With EF Core, you deal with database schema changes by using migrations. When you first create the database, you create a migration that contains the initial definition of the … Read more

EF Core – How to create a database and a table

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In this article, I’ll show how to use EF Core to create a database with one table in it. At the end, I’ll show a standalone console app that inserts a record into this database. Note: I’ll be using SQL Server. I haven’t tried this with other database providers. Please leave a comment if you’re … Read more

SQL Server – DB is currently in use

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Problem Let’s say you’re running in a test/dev environment and you’re trying to alter the database. For example, you may be trying to drop the database: But you get the following error message and your command fails: Cannot drop database “CSI” because it is currently in use. This means there are other open connections on … Read more

SQL Server – Getting and storing date/time

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In this article, I’ll show built-in functions in SQL Server for getting the current datetime and how to get individual parts of the datetime (such as the year). Then show I’ll show how to store datetimes using the four different date/time data types (date, time, datetime2, and datetimeoffset). Getting the current datetime SQL Server has … Read more

SQL Server – Bad SELECT query performance due to missing indexes

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When you have a slow SELECT query, the most likely cause of the problem is that you’re missing an index. When your table has lots of data, having the right indexes will make a difference in the performance. Without indexes, SQL Server has to scan through your entire table to find the rows that match … Read more

C# – How to use SqlBulkCopy to do a Bulk Insert

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If you find yourself doing SQL Inserts in a loop, you may want to consider doing a Bulk Insert instead. You can use SqlBulkCopy to do a Bulk Insert from C#. Make sure to prove you have a performance problem before switching your code to use Bulk Insert. Like any optimization, it adds complexity. In … Read more

C# – Mapping nullable columns with SqlDataReader

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When you have a database table with null columns, and you’re using SqlDataReader to map the results, there are a few things to do: Use nullable types in the model class. Example: instead of int use int? so the value can be null. Use SqlDataReader.IsDBNull() to check if you need to set the value to … Read more

C# – Using SqlDataReader to process multiple result sets

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In this article I’ll show how to use the SqlDataReader ADO.NET class in two scenarios involving multiple result sets: Batches – When you execute multiple SELECTs in a single query. Each SELECT returns a different result set. You use a single reader to process the batch. Nested Queries – When you use multiple SqlDataReaders on … Read more

Modifying JSON in SQL Server

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There are two ways to modify JSON data in a SQL Server table: Use the JSON_MODIFY() function in an UPDATE statement to change individual properties inside the JSON data. Completely replace the JSON data with a regular UPDATE statement. In this article, I’ll show how to insert, update, and delete JSON data by using the … Read more

Querying JSON in SQL Server

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In SQL Server 2016 they added support for handling JSON data. You can add JSON data, query it, and modify it. The JSON API in SQL Server is well-suited for simple scenarios where you only need to do basic querying and manipulation. For advanced querying, the SQL Server JSON API gets complicated and hard to … Read more