Function sql_placeholders 

pub fn sql_placeholders(count: usize) -> String

Build a comma-separated list of SQL placeholders with pre-allocated capacity.

For n items, produces “?,?,?…” (n “?” with n-1 “,”). Uses pre-sized String to avoid reallocations.

Examples

assert_eq!(sql_placeholders(0), "");
assert_eq!(sql_placeholders(1), "?");
assert_eq!(sql_placeholders(3), "?,?,?");