Function count_all 

pub fn count_all() -> Expr

Creates aggregation to count all rows.

In SQL this is SELECT COUNT(*) ...

The expression is equivalent to COUNT(*), COUNT(), COUNT(1), and is aliased to a column named "count(*)" for backward compatibility.

Example

// create `count(*)` expression
let expr = count_all();
assert_eq!(expr.schema_name().to_string(), "count(*)");
// if you need to refer to this column, use the `schema_name` function
let expr = col(expr.schema_name().to_string());