import { ExpressionToken } from '../expression/expression-token';
import { ColumnType } from '../column';
/**
 * Database functions are typed by column type, so that users
 * 	gain strong typing when using functions, i.e. the user
 * 	can't assign a date function to a bool column.
 */
export type DatabaseFunctionReturnType = keyof typeof ColumnType;
export declare enum DatabaseFunctionKeys {
    AVERAGE = 0,
    COUNT = 1,
    MIN = 2,
    MAX = 3,
    SUM = 4,
    CURRENT_TIMESTAMP = 5,
    DATE = 6,
    YEAR = 7,
    UUID = 8
}
export interface DatabaseFunction<T extends DatabaseFunctionReturnType = DatabaseFunctionReturnType> {
    fn: DatabaseFunctionKeys;
    type: T;
    params?: any;
}
/**
 * A token is returned by database functions, so that it can be
 * 	interpreted during sql generation.
 */
export type DatabaseFunctionToken<T extends DatabaseFunctionReturnType = DatabaseFunctionReturnType> = ExpressionToken & DatabaseFunction<T>;