The LAG function returns data from preceding rows.
LAG uses the following syntax:
LAG ( Column name, Offset, Default )
LAG returns the value at an offset number of rows before the current row. Use the LAG function to compare values in the current row with values in a previous row. Use the following arguments with the LAG function:
Column name. The column name whose value from the prior row is to be returned.
Offset. The number of rows preceding the current row from which the data is to be retrieved. For example, an offset of "1" accesses the previous row, and an offset of "3" accesses the row that is three rows before the current row.
Default. The default value to be returned if the offset is outside the scope of the partition. If you do not specify a default, the default is NULL.
For more information about the LAG function, see the