There are three types of window functions including value window functions, aggregation window functions, and ranking window functions. Value window functions # FIRST_VALUE()

SQL LAG() is a window function that provides access to a row at a specified physical offset which comes before the current row. In other words, by using the LAG() function, from the current row, you can access data of the previous row, or from the second row before the current row, or from the third row before current row, and so on.

The FIRST_VALUE() is a window function that returns the first value in an ordered set of values. Here’s the syntax of the FIRST_VALUE() function: FIRST_VALUE(expression) OVER ( partition_clause order_clause frame_clause ) Code language: SQL (Structured Query Language) ( …

The ROW_NUMBER() is a window function that assigns a sequential integer number to each row in the result set. Here’s the syntax of the ROW_NUMBER() function: ROW_NUMBER() OVER ( [PARTITION BY expr1, expr2,...]

SQL LEAD() is a window function that provides access to a row at a specified physical offset that follows the current row. For example, by using the LEAD() function, from the current row, you can access data from the next row, the second row that follows the current row, the third row that follows the current row, and so on.

In SQL, a window function allows you to calculate across table rows that are somehow related to the current row. A window function uses the OVER clause to define the window or a set of rows on which a window function operates. The OVER clause includes optional PARTITION BY and ORDER BY clause. Here’s the basic syntax of a window function that ...

The RANK() function is a window function that assigns a rank to each row in the partition of a result set. The rank of a row is determined by one plus the number of ranks that come before it. The syntax of the RANK() function is as follows

The DENSE_RANK() is a window function that assigns a rank to each row in partitions with no gaps in the ranking values. If two or more rows in the same partition have the same values, they receive the same rank.

The PERCENT_RANK() is a window function that calculates the percentile ranking of rows in a result set. The syntax of the PERCENT_RANK() function is as follows: PERCENT_RANK() OVER ( PARTITION BY expr1, expr2,...

This section provides you with many built-in SQL functions including aggregate functions, date functions, string functions, and window functions.