Examples
SQL Window Function
SQL Window Function Example
Window function with ROW_NUMBER and PARTITION BY ranks rows.
Introduction to SQL Window Functions
SQL Window Functions are powerful tools used to perform calculations across a set of table rows related to the current row. Unlike aggregate functions, they do not collapse rows into a single result. Instead, they provide a detailed view by adding aggregated values to each row. This post will focus on using the ROW_NUMBER function in combination with PARTITION BY to rank rows within a partition.
Understanding ROW_NUMBER and PARTITION BY
The ROW_NUMBER function is used to assign a unique sequential integer to rows within a partition of a result set. The numbering is ordered by a specified column. When combined with PARTITION BY, it allows you to reset the row number for each partition.
For instance, if you have sales data and you want to rank sales within each region, you can use ROW_NUMBER with PARTITION BY to achieve this.
SQL Example: Ranking Sales by Region
Let's consider a database table named sales with the following columns: id, region, salesperson, and total_sales. We want to rank salespeople within each region based on their total sales.
In this SQL query:
ROW_NUMBER() OVER (PARTITION BY region ORDER BY total_sales DESC): This assigns a rank to each salesperson within their region based on theirtotal_sales, sorted in descending order.PARTITION BY region: This clause divides the result set into partitions by theregioncolumn.ORDER BY total_sales DESC: This determines the order of ranking within each partition.
The result will show each salesperson's rank within their respective region.
Benefits of Using Window Functions
Window functions are advantageous because they provide a more detailed view of your data without collapsing it into a single row. They allow you to perform complex calculations and rankings like the one demonstrated, which can be invaluable for analytical queries.
SQL Examples
- Simple Select
- Filtered Query
- Sorted Query
- Joined Query
- Aggregate Report
- Subquery Example
- Correlated Subquery
- Insert Data
- Update Data
- Delete Data
- Create Table
- View Creation
- String Manipulation
- Date Calculations
- JSON Query
- Window Function
- CTE Example
- Pivot Report
- Union Query
- Paginated Query
- Hierarchy Query
- Sales Report
- User Management
- Inventory Query
- Search Query
- Dynamic Filter
- Error Handling
- Data Export
- Data Import
- Table Backup
- Query Logging
- Conditional Aggregation
- Cross Tabulation
- Previous
- JSON Query
- Next
- CTE Example
