![]() At the same time, using this syntax, the query just returns ‘ Employee’. ![]() However, we wanted to obtain the value ‘ Manager’ if the employee is also a manager. All values in the last column are ‘ Employee’ only. ![]() This is what the code should look like: SELECTĮ.emp_no > 109990 The Problem with IS NULL and IS NOT NULLĪs shown in the picture below, the query didn’t return the correct result. Now, just as an exercise, try rewriting and executing the same query by removing ‘ dm.emp_no’ from the line with the WHEN keyword and placing it right after CASE. Else the returned value will be ‘ Employee’.Īnd, as we run this query, that’s exactly the output we obtain, as you can see in the picture below. It says that if ‘ dm.emp_no’ is not null, then SQL will return the value ‘ Manager’. WHEN dm.emp_no IS NOT NULL THEN 'Manager'Ĭonsider the SQL CASE statement within this query. For instance, consider the following query: SELECT We must say that this technique wouldn’t work in all cases, though. Then, we should write the corresponding value after the WHEN keyword, without using ’=’. This means that we can obtain the same exact result by putting the name of the column once - right after the word CASE. If we write the following code, we should retrieve the same output: SELECTĪs shown in the picture above, we achieved what we wanted. Is There Another Way to Write an SQL CASE Statement? Let’s see what happens after we run the following query: SELECT As it name suggests, it shows where the CASE statement will terminate. After that, we have ELSE as a final expression if all conditions mentioned so far turn out false.įurthermore, END is an obligatory part of the syntax. Therefore, observe how the syntax of the CASE construct starts with the keyword CASE followed by WHEN and a conditional expression containing the word THEN. In this example, when the value of the column is ‘M’, we will return ‘Male’ and if it’s ‘F’ – ‘Female’. Well, here’s how the SQL CASE statement can help. Side note: If you haven’t downloaded the ‘employees’ database that we will be using, make sure you download it here. It contains the values ‘M’ and ‘F’.īut what if we want to return some more meaningful values instead? Its syntax can vary depending on what we want to show.Īs we know, in our ‘ employees’ table we have a column called ‘ gender’, filled with data of the ENUM type. It is used within a SELECT statement when we want to return a specific value, based on some condition. However, let’s focus on the SQL CASE statement. So, MySQL is a rich language and there are many ways a condition can be expressed.įor instance, you may want to retrieve a type of query output in case a specific condition has been satisfied And another type of output in case it has not been satisfied.Īs an example, remember that one way to apply such technique is through the COALESCE or the IFNULL functions. Side note: If you want to read about another advanced SQL topic, dive into our tutorial on MySQL indexes. ![]() In this tutorial, we will be talking about a conditional construct called the SQL CASE statement. ![]()
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