pub fn validate_scalar_sql(sql: &str) -> Result<(), ValidationError>Expand description
Validate a scalar SQL string: runs the dry-run and checks the result
projects exactly one column. Used by query_scalar!.
Does not require a struct registration — scalars project a single column
of a primitive type without mapping to a struct. However, tables referenced
by the SQL still need to be registered via derive(Table) #[hyperdb(register)]
for compile-time validation to work; unregistered tables produce a
TablesNotRegistered diagnostic.
§Errors
Returns a ValidationError if the SQL is invalid, references an
unregistered table, or the result schema does not have exactly one column.