Functions
Functions calculate values or provide rows to a query. Their role determines how they are called:
| Family | Role |
|---|---|
| Scalar | Calculate one value from expressions in the current row. |
| Aggregate | Calculate one result from several input rows or each GROUP BY group. |
| Table | Provide rows in a FROM clause. |
| Window | Calculate a value using related rows without collapsing the input. |
Names ignore ASCII case; use each documented snake_case spelling. Argument counts, accepted types, NULL behavior and errors are defined per function.
The server exposes descriptive metadata in system.functions, including before a database is selected. That catalog is descriptive, so a missing legacy entry is not proof that a function is unavailable.