func (nz *normalizer) WalkSelect(node SQLNode) (bool, error) {
	switch node := node.(type) {
	case *SQLVal:
		nz.convertSQLValDedup(node)
	case *ComparisonExpr:
		nz.convertComparison(node)
	}
	return true, nil
}
func (nz *normalizer) WalkSelect(node SQLNode) (bool, error) {
	switch node := node.(type) {
	case *SQLVal:
		nz.convertSQLValDedup(node)
	case *ComparisonExpr:
		nz.convertComparison(node)
	}
	return true, nil
}
// WalkSelect normalizes the AST in Select mode.