In order to understand the problem and solution better, let's create a sample database with some values. Let's first see, how to use ISNULL() to replace NULL String to empty String in SQL SERVER. Replacing NULL with blank in SQL SERVER - ISNULL() Example It''s a great course to learn T-SQL concepts, functional, and SQL Server basics. COALESCE(column, column2, ''), so if the column is null then it will use column2 and if that is also null then it will use empty String.įor SQL Server and T-SQL beginners, I also recommend Microsoft SQL for Beginners online course by Brewster Knowlton on Udemy. The only difference between them is that ISNULL() is Microsoft SQL Server-specific but COALESCE() is the standard way and supported by all major databases like MySQL, Oracle, and PostgreSQL.Īnother difference between them is that you can provide multiple optional values to COALESCE() e.g. Similarly, COALESCE(column, '') will also return blank if the column is NULL. Both functions replace the value you provide when the argument is NULL like ISNULL(column, '') will return empty String if the column value is NULL. There are two ways to replace NULL with blank values in SQL Server, function ISNULL(), and COALESCE(). To prevent this, you can replace NULL with empty String while concatenating. In SQL Server, when you concatenate a NULL String with another non-null String the result is NULL, which means you lose the information you already have. You could easily do this on your blog.We often need to replace NULL values with empty String or blank in SQL e.g. This post took about 15 minutes to write. This is how I’d solve the issue, and decided to share that knowledge more widely, both to help others and also provide an example of where I might have a hiring manager ask me about this from noticing my blog. This was a post inspired by a question I saw. , ISNULL(CAST(oh.OrderID AS VARCHAR(20)), 'N/A') AS OrderIDīoth cases clean up the NULL values with something that makes more sense to a person looking at the data in a report. I could also return a string if I cast all OrderIDs to strings, as shown below. This is because the result set is a numeric, and I need these types to match. , ISNULL(oh.OrderNote, 'No orders placed') AS OrderNote Here’s a better query that replaces one value with a NA and another with a blank. I’ll use ISNULL here and in another post look at COALESCE. ISNULL is for a single expression and replaces NULL with value, while COALESCE works by returning the first non-NULL expression. I can use a couple of functions to look for a NULL value in my results. This works, but really, I’d like to clean up the results to show something better. Using the left join below, we see all customers with their corresponding orders. If we use an inner join, we only see customers with orders. Potentially, we have customers without orders. INSERT dbo.OrderHeader (CustomerID, OrderNote) ( OrderID INT NOT NULL IDENTITY(1,1) CONSTRAINT OrderHeaderPK PRIMARY KEY ( CustomerID INT NOT NULL IDENTITY(1,1) CONSTRAINT CustomerPK PRIMARY KEY Use this code: DROP TABLE IF EXISTS dbo.Customer This is common, where we have customers that we might add as prospects in some CRM type system. Let’s create a table of customers and orders with a few values in each. I realized this is one of those simple things that people new to SQL might not get.Īnother post for me that is simple and hopefully serves as an example for people trying to get blogging as #SQ LNewBlogger s. I saw someone ask a question on how to replace NULL in a left join and decided to write a post.
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