For an instructor lead, in-depth look at learning SQL click below.
Databricks is a powerful tool built for sophisticated data analysis, and when combined with SQL, it offers unprecedented business intelligence capabilities. In this blog post, we will cover several advanced SQL techniques you can use in Databricks to unlock these powerful features.
1. Manipulating Data with SQL Functions
SQL functions provide the ability for complex manipulation of data. Let’s take a look at few examples:
|
1 2 3 4 5 6 7 8 |
-- Using STRING_SPLIT Function SELECT value FROM STRING_SPLIT('John,Doe,USA', ',') -- Using FORMAT Function SELECT FORMAT (GETDATE(), 'd', 'en-US' ) as 'Date' |
2. Window Functions
Window functions are powerful tools which can perform a calculation across a set of table rows related to the current row.
|
1 2 3 4 5 6 7 8 9 10 11 |
-- Using ROW_NUMBER SELECT *, ROW_NUMBER() OVER(ORDER BY Sales) as RowNumber FROM SalesTable -- Using RANK SELECT *, RANK() OVER(ORDER BY Sales) as SalesRank FROM SalesTable |
3. Advanced Joins
SQL JOIN clause is used to combine rows from two or more tables, based on a related column. Here are few advanced JOIN techniques:
|
1 2 3 4 5 6 7 8 9 10 11 12 13 |
-- Using FULL OUTER JOIN SELECT Customers.CustomerName, Orders.OrderID FROM Customers FULL OUTER JOIN Orders ON Customers.CustomerID = Orders.CustomerID -- Using RIGHT JOIN SELECT Customers.CustomerName, Orders.OrderID FROM Customers RIGHT JOIN Orders ON Customers.CustomerID = Orders.CustomerID |
4. Recursive Queries
Recursive queries are an efficient way of dealing with hierarchical data. The following example creates a common table expression (CTE) and uses a recursive integrated function to populate the CTE with hierarchical data.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 |
-- Recursive CTE WITH EmployeeHierarchy AS ( SELECT EmployeeId, FirstName, LastName, ManagerId FROM Employee WHERE ManagerId IS NULL UNION ALL SELECT E.EmployeeId, E.FirstName, E.LastName, E.ManagerId FROM Employee AS E INNER JOIN EmployeeHierarchy AS EH ON E.ManagerId = EH.EmployeeId ) SELECT * FROM EmployeeHierarchy |
In conclusion, with knowledge of advanced SQL techniques and Databricks, you will be able to dramatically increase the sophistication and power of your data extraction and manipulation capabilities.