Function greatest 

pub fn greatest<'a, V, L, R>(
    left: L,
    right: R,
) -> SQLExpr<'a, V, L::SQLType, <L::Nullable as NullAnd<R::Nullable>>::Output, <L::Aggregate as AggOr<R::Aggregate>>::Output>
where
    V: SQLParam + 'a,
    V::DialectMarker: PostgresNullSupport,
    L: Expr<'a, V>,
    R: Expr<'a, V>,
    L::SQLType: Compatible<R::SQLType>,
    L::Nullable: NullAnd<R::Nullable>,
    R::Nullable: Nullability,
    L::Aggregate: AggOr<R::Aggregate>,
    R::Aggregate: AggregateKind,

GREATEST - returns the largest of the given values (PostgreSQL).

Both arguments must have compatible types. PostgreSQL ignores NULL inputs, so GREATEST(1, NULL) returns 1. The result is only NULL when all inputs are NULL.

Example

use drizzle_core::expr::greatest;

// Clamp to minimum of 0
let score = greatest(users.score, 0);