postgresql replace null with empty string

Here is the screenshot of SQL queries from Microsoft SQL SERVER 2014 database to give you full view: Following SQL query uses COALESCE to do that:ĬOALESCE(first_name,last_name, '') as first_name,ĬOALESCE(last_name, first_name, '') as last_name,ĬOALESCE(first_name, '') + COALESCE(last_name, '') as full_name For example, in this scenario, let's display the value of last_name if first_name is NULL and the value of first_name if last_name is NULL in the report. You can use this technique to provide sophisticated default values in your reports. You can use COALESCE() to instruct using the value of another column if the target column is NULL and if that is also null then use the third column and so on. Let me show you another use of COALESCE() function while we are using it. SELECT first_name, last_name, COALESCE(first_name, '') + COALESCE(last_name, '')

In this example, you don't need to do anything, just replace ISNULL() with COALESCE() and you are done, as shown in the following SQL query: Remember, COALESCE() is a standard function and whenever you can use COALESCE() you should be using it. In the earlier example, you have learned how to use ISNULL() to replace NULL values with blank in SQL SERVER, let's see how can we use COALESCE() to do the same. Using COALESCE() to replace NULL with empty String in SQL SERVER You can see that even though one of the joining columns is NULL but full_name is not NULL anymore because ISNULL() is replacing NULL values with a blank. SELECT first_name, last_name, ISNULL(first_name, '') + ISNULL(last_name, '') In order to avoid that and to replace the NULL with empty String, let's use ISNULL() method in our SQL query: You can see that full_name is NULL for the second and third record because for them either first_name or last_name is NULL. SELECT first_name, last_name, first_name + last_name AS full_name FROM #People

Now let's display the first name, last name and full name from #People table, where the full name is nothing but a concatenation of first and last name. IF OBJECT_ID( 'tempdb.#People' ) IS NOT NULL DROP TABLE #People ĬREATE TABLE #People (first_name varchar(30), last_name varchar(30)) INSERT INTO #People VALUES ('Joe','Root') INSERT INTO #People VALUES ('Mary', NULL) INSERT INTO #People VALUES (NULL, 'Broad') - cleanup - DROP TABLE #People 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. We often need to replace NULL values with empty String or blank in SQL e.g.

Postgresql replace null with empty string