MySQL Window Functions are powerful tools that allow you to perform calculations across a set of table rows related to the current row. These functions are particularly useful when you need to analyze and derive insights from your data based on specific ordering or partitions within your result set. Here are some commonly used MySQL Window Functions:
| Function | Description |
|---|---|
| CUME_DIST | Computes the cumulative distribution of a value within a group of rows. It represents the relative position of a row within the result set. |
| DENSE_RANK | Assigns a rank to each distinct row within the result set, without leaving gaps in the ranking, even if there are ties. |
| RANK | Assigns a unique rank to each row within its partition, with gaps between ranks for equal values. This can be useful for calculating the exact position of a row within the ranked set. |
| FIRST_VALUE | Returns the value of the argument from the first row of the window frame. It’s useful for obtaining the initial value of a series or identifying the first occurrence of a particular condition. |
| LAST_VALUE | Returns the value of the argument from the last row of the window frame. It’s useful for getting the final value of a series or identifying the last occurrence of a particular condition. |
| LAG | Returns the value of the argument from a row lagging the current row within the partition. It takes an offset parameter that specifies the number of rows to lag. This can be used to compare values with previous rows. |
| LEAD | Returns the value of the argument from a row leading the current row within the partition. It also takes an offset parameter. This can be used to predict or extrapolate future values based on historical data. |
| NTH_VALUE | Returns the value of the argument from the Nth row of the window frame. It takes an offset parameter and can be used to identify specific rows within a group of values. |
| NTILE | This function divides the partition into a specified number of buckets and returns the bucket number of the current row. It’s useful for ranking rows into groups based on a specific criterion. |
| PERCENT_RANK | Computes the relative rank of a row within a result set as a percentage. |
| ROW_NUMBER | Assigns a unique number to each row within a partition of the result set. |
MySQL Window Functions provide a versatile way to analyze and aggregate data within specific partitions or window frames, offering greater flexibility and efficiency compared to traditional aggregate functions. They are particularly useful in scenarios where you need to perform calculations that involve a dynamic range of rows around each data point in your result set.