SQL
General-Purpose Window Functions
<div class="nostroke_table"></div>  
|   |   |
|:--|:--------|
| **Description** |Returns `expr` evaluated at the row that is `offset` rows (among rows with a non-null value of `expr` if `IGNORE NULLS` is set) before the current row within the window frame; if there is no such row, instead return `default` (which must be of the Same type as `expr`). Both `offset` and `default` are evaluated with respect to the current row. If omitted, `offset` defaults to `1` and default to `NULL`. |
| **Return Type** | Same type as `expr` |
| **Aliases** | `lag(column, 3, 0)` |