SQL LAG Function: Uses & Examples

In SQL, the LAG function is used to access data from the previous row in order to compare or calculate with the data in the current row. The main purposes of the LAG function include:

1. Calculate the difference or growth rate between the current row and the previous row.
2. Detect changes or trends between the current row and the previous row.
3. Calculate the time difference or time interval.
4. Access the data from the previous row for further computation or analysis.
5. Aggregating calculations based on the data from the previous line using sliding windows.

In general, the LAG function can help analysts and developers better understand and interpret changes and trends in data, thereby supporting more in-depth data analysis and decision-making.