/**
 * SQL Tagged Template Literal
 *
 * Marks a string as a SQL expression rather than a column reference.
 * Used to distinguish between:
 * - Simple column: 'region' (string)
 * - SQL expression: sql`DATE(created_at)` (SQLExpression)
 *
 * @example
 * ```typescript
 * dimensions: {
 *   region: 'region',  // Simple column reference
 *   date: sql`DATE(created_at)`,  // SQL expression
 *   hour: sql`toHour(created_at)`  // SQL expression
 * }
 * ```
 */
/**
 * Represents a SQL expression with metadata
 */
export interface SQLExpression {
    readonly __brand: 'SQLExpression';
    readonly sql: string;
    readonly raw: boolean;
}
/**
 * Tagged template literal for SQL expressions
 *
 * @param strings - Template string array
 * @param values - Interpolated values
 * @returns SQLExpression object
 */
export declare function sql(strings: TemplateStringsArray, ...values: unknown[]): SQLExpression;
/**
 * Type guard to check if a value is a SQLExpression
 *
 * @param value - Value to check
 * @returns True if value is a SQLExpression
 */
export declare function isSQLExpression(value: unknown): value is SQLExpression;
/**
 * Convert a value to a SQL string
 * - If it's a SQLExpression, return the sql property
 * - If it's a string, return it as-is (assumed to be a column name)
 * - Otherwise, throw an error
 *
 * @param value - Value to convert
 * @returns SQL string
 */
export declare function toSQLString(value: string | SQLExpression): string;
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