The ALTER AGGREGATE statement in SQL is used to modify an existing aggregate function in databases that support this functionality, such as PostgreSQL. This command allows you to change properties of the aggregate function, such as its name, owner, or its transition and final functions, among other attributes.
Here’s a general syntax for the ALTER AGGREGATE statement:
ALTER AGGREGATE [schema_name.]aggregate_name (parameter_types)
[ owner TO new_owner ]
[ SET ( option = value ) ]
[ ... ];
Parameters
- schema_name: The schema where the aggregate function is defined. This is optional; if omitted, the current schema is used.
- aggregate_name: The name of the aggregate function you want to modify.
- parameter_types: The data types of the arguments that the aggregate function takes, enclosed in parentheses. This is required to identify the correct aggregate if there are overloads.
- owner TO new_owner: If you want to change the owner of the aggregate function.
- SET ( option = value ): To set various options related to the aggregate, such as its behavior, cost, etc.
Example
Here's a simple example that demonstrates how to change the owner of an existing aggregate function:
ALTER AGGREGATE my_schema.my_aggregate_function(integer)
OWNER TO new_owner;
Another Example
If you want to change the behavior or other properties of the aggregate, you could modify it like this:
ALTER AGGREGATE my_schema.my_aggregate_function(integer)
SET (parallel = safe);
Important Notes
1. Permissions: You need to have the necessary permissions to modify an aggregate function.
2. Dependencies: Be aware that changing the properties of an aggregate function may affect other database objects that depend on it.
3. Database-Specific: The syntax and capabilities of ALTER AGGREGATE can vary between different SQL database systems, so consult the documentation specific to your database for precise details.
In summary, ALTER AGGREGATE is a powerful command that allows you to modify how an existing aggregate function behaves or is defined in your database.