Function count 

pub fn count<'a, V, E>(expr: E) -> SQLExpr<'a, V, BigInt, NonNull, Agg>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,

COUNT(expr) - counts non-null values.

Returns a BigInt, NonNull (count is never NULL), Aggregate expression. Works with any expression type.

Example

use drizzle_core::expr::count;

let count = count(users.email);
// Generates: COUNT("users"."email")