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Articles about using the SQL Server database engine as a .NET developer.
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
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
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
SqlDataReader returns a DBNull object when a column is null. This isn’t the same as a C# null. You can check if the column is null by comparing it with DBNull.Value or by using SqlDataReader.IsDBNull(). Here’s an example showing these two ways of checking if a column is null: After checking if the column is … Read more
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
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
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
To execute a query against all tables in a database, you can use the sp_msForeachTable stored proc, like this: Note: The ? is a placeholder for the table name. In this article I’ll show two examples of using sp_msForeachTable. Example – Get record counts for all tables This query saves record counts to a temp … Read more
There are multiple ways to increment ids in SQL Server: IDENTITY columns SEQUENCEs (added in SQL Server 2012) Atomic UPDATEs with the OUTPUT clause In this article I’ll show the third way – using an atomic UPDATE with OUTPUT. Tables – Ids and Users I have the following two tables – Ids and Users: Stored … Read more
Here’s how to execute a SQL query and export the results to a CSV file: If Invoke-SqlCmd is missing, install the SqlServer module If it’s complaining about not having Invoke-SqlCmd available, you will need to install the SQL Server PowerShell module. 1 – Run PowerShell as administrator 2 – Add Microsoft’s PSGallery as a trusted … Read more
There are two ways to filter GROUP BY results: In other words, WHERE controls which rows will be considered for grouping, GROUP BY groups the filtered rows, and then HAVING filters the groups. I’ll show examples below. Example – Using WHERE with GROUP BY Let’s say you have the following table and you want to … Read more
Let’s say you have a SQL Query that uses IN and you want to execute it using Dapper. Your query looks something like this: Here’s how you’d execute that with Dapper: Then you’d call it like this: There are two key things to notice about this: You have to exclude the parentheses. I specified one … Read more
In SQL Server Management Studio (SSMS), when you right-click on a table, it’ll show you the commands “Select Top 1000 Rows” and “Edit Top 200 Rows” in the context menu. You can change the number of rows these commands return. Here’s how to make this change: Now when you right-click a table, it’ll show the … Read more
Problem You’re trying to save a table change in SSMS and you get the error message: Saving changes is not permitted. The changes that you have made require the following tables to be dropped and re-created. You have either made changes to a table that can’t be re-created or enabled the option Prevent saving changes … Read more
Problem I am executing a SQL query and trying to set a datetime column to DateTime.MinValue. I’m getting the following exception: System.Data.SqlTypes.SqlTypeException: ‘SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.’ The problem is that DateTime.MinValue is 1/1/0001 12:00:00 AM and the SQL Server DateTime minimum value is 1/1/1753 12:00 AM. Solution … Read more
Problem When I execute a SQL query I’m getting the following error: Conversion failed when converting date and/or time from character string. The query is using ORDER BY with CASE with a passed in parameter called @OrderBy. Solution Use a separate CASE statement for each possible value (instead of one CASE with multiple WHENs).
Problem You have a SQL query like this: While executing this you get the following error: ‘CREATE/ALTER PROCEDURE’ must be the first statement in a query batch Solution The error message says it all: the CREATE PROCEDURE statement cannot be executed after other queries in the same batch of queries. The solution is to execute … Read more
How do you check for new records in a database and react to the new data? You really only have two options: Poll for changes every X seconds Use query notifications to be notified when new data is inserted In this article I’ll show you how to configure query notifications so that your application receives … Read more
Imagine you’re in the middle of Millennium Park in Chicago. You want some coffee, but want a good deal on it. You open an app and see the nearest coffee shops offering deals to anyone with this app. How did this app know the distance from you to the coffee shops? This article will show … Read more
Problem When entering the sa password while installing SQL Server you get the following error: “The specified sa password does not meet strong password requirements.“ Solution If the computer is on a domain Not on a domain
