Required fields are marked *. This is how the employee table I’m going to use for the example looks like: Now suppose I am asked to create a query that tells me the number of employees that were hired in the years of 2014 and 2015 for each department. I’m glad you find my articles helpful. In SQL, Pivot and Unpivot are relational operators that are used to transform one table into another in order to achieve more simpler view of table. In this case, we will get information about an employee, his department code and salary he gets. So, I needed an inline view because where I have the “YEAR” in the pivot clause, it is mandatory that you use a column. As you can see, now I have 2 rows for each department. I can’t do a simple count grouped by department, because it would count the number of employees of each department, regardless of the date in which they were hired. Here is my DEPARTMENT table. Since there is a condition involved here, it sounds like a job for a CASE expression. I’m glad you liked it . Open in new window. [col2] As col3. By default, the UNPIVOT operation excludes null-valued rows, therefore, you don’t see any NULL in the output. Learn how your comment data is processed. [col2] from (select DOLLARVALUES_001, DOLLARVALUES_002, DOLLARVALUES_003 from, (select * from PHDOLLARS where PHSMRANGE ='0501C200') p ) p, ([col2] for [col1] IN (DOLLARVALUES_001, DOLLARVALUES_002, DOLLARVALUES_003)), select PVTb. As you can see, I have birth_year and hire_year in the FOR clause in line 10, and I have the combination of values I’m interested in, in the IN clause in line 11. subquery = results of subquery can be used as values of columnname2. The UNPIVOT clause is opposite to the PIVOT clause except that it does not de-aggregate data during the transposing process.
So we may expect almost double reduction in the number of I/O operations. I like your articles. Please use ide.geeksforgeeks.org, generate link and share the link here. SQL vs NoSQL: Which one is better to use? [col1], a. The following illustrates the syntax of Oracle UNPIVOT clause: The INCLUDE | EXCLUDE NULLS clause allows you to include or exclude null-valued rows. As you can imagine, Unpivot help us do the opposite operation of Pivot. The FIRST and LAST functions in Oracle SQL, Pairwise Comparisons With Subqueries in Oracle SQL, How to Change Oracle SQL Developer Language. Change ), You are commenting using your Twitter account. We can use INCLUDE NULLS to print that data. Let us understand PIVOT by simple example: If we want breakdown my emp_code then add it in SELECT CLAUSE. This is the default behavior, but if you want to get all of the rows, even if they have NULL in the original data, you just need to add “INCLUDE NULLS” in the UNPIVOT clause: I modified the Unpivot clause in line 3, and as you can see, with this change now I have both categories for those departments. There’s another thing to notice here: I have 2 rows for ACCOUNTING, 2 for MARKETING and 2 for IT and HUMAN RESOURCES, but I have only one for REGULATORY AFFAIRS and CUSTOMER SERVICE. columnname1, columnname2 = Columns of table And I did all of this in the same query, which is pretty awesome! UNPIVOT command (introduced in Oracle 11g) came to resque. Summary: in this tutorial, you will learn how to use the Oracle UNPIVOT clause to transpose columns to rows. In this article, I'll be using the AdventureWorks demo database. Change ), You are commenting using your Facebook account. Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. Change ). And I can also add an alias for the values inside the parentheses, for example: And as you see, those aliases are also used to construct the final column names. This produces the same results than our previous query, but this query looks simpler, don’t you think? The number of estimated row, selected from DEB_ROWS table, is a bit more precise that in previous SELECT (17M instead of 16M) but in both cases the estimation is quite good. So I've got these two queries that pull different data from the same table and use the UNPIVOT statement to rearrange the data. Example-1: If you look at the data in the department table again, you can see that for those departments I have NULL in the LAST_EMPLOYEE_ID column, and that is why I don’t have that category in my UNPIVOTed results. Our community of experts have been thoroughly vetted for their expertise and industry experience.
The results are the same as the standard LEFT OUTER JOIN example above, so we won’t include them here. So I've got these two queries that pull different data from the same table and use the UNPIVOT statement to rearrange the data.
I’m going to call it “EMPLOYEES_HIRED” to show you how this alias is used. expression_1, expression_2 = values of columnname2 This is a text widget, which allows you to add text or HTML to your sidebar. The only difference in these queries is the where statement. They are called inline views. Bottom line.
Think about for a moment. Now I have 2 columns for each department: One for the salaries and one for the employees. Fortunately, you now have a great new feature called PIVOT for presenting any query in the crosstab format using a new operator, appropriately named pivot. Subscribe to be informed about new posts, tips and more awesome things. UNPIVOT command (introduced in Oracle 11g) came to resque. Being an avid blogger, I would like to inform you about my productivity and motivational blog XpressPlanet.com. I rewrote the cursor.
PIVOT and UNPIVOT in Oracle. These queries look like this: This award recognizes someone who has achieved high tech and professional accomplishments as an expert in a specific topic. Edit them in the Widget section of the, Michael Bialik – Performance Consultant/DBA, Oracle Data Provider (ODP.NET) – using array binds to improve performance, Using PL/SQL to check if directory exists on server. Very good concept on the Pivot and unpivot functions, very nicely articulated for easy understanding – Thank you so much CARLOS, i am following all your articls, you are doing great stuff — keep doing your innovative work and expecting more articles from you.. Calling PL/SQL Stored Functions in Python, Deleting Data From Oracle Database in Python. Now, go ahead and have some fun practicing them. © 2020 Oracle SQL Tips, Tricks and Hacks. (Unlock this solution with a 7-day Free Trial). I rewrote the cursor.
In a similar way, for the row that includes data only for employees who earn less than 3000, the type column will say ‘EMPLOYEES WHO EARN LESS THAN 3000’, and the EMPLOYEES column in the result will have the data from the EMPLOYEES_3000 column from my pivoted_employee table, and the salaries column will have data from the SALARIES_3000 column. To show you why you might need to do this type of operation, I’m going to show you a very simple example. As expected the result of UNPIVOT doubles the number of rows (for each row of DEB_ROWS table it generates 2 rows). Now, we use the same table “geeksforgeeks” created in the above example and apply the Unpivot operator to our Pivoted table. Please keep that in mind. Converting Rows Into Columns (The Pivot Clause), Converting Columns Into Rows (The Unpivot Clause).
Pivot function works similar to transpose function in Microsoft Excel.