export type Expression = SQLExpression | AggregateExpression;
/** A custom SQL expression. */
export interface SQLExpression {
    /**
     * A SQL expression string to derive a new column value.
     * Embedded Param references, such as `$param + 1`, are supported.
     * For expressions with aggregate functions, use *agg* instead.
     */
    sql: string;
    /**
     * A label for this expression, for example to label a plot axis.
     */
    label?: string;
}
/** A custom SQL aggregate expression. */
export interface AggregateExpression {
    /**
     * A SQL expression string to calculate an aggregate value.
     * Embedded Param references, such as `SUM($param + 1)`, are supported.
     * For expressions without aggregate functions, use *sql* instead.
     */
    agg: string;
    /**
     * A label for this expression, for example to label a plot axis.
     */
    label?: string;
}
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