errx

var (
	// ErrMissingIdentity indicates SQL generation/execution cannot proceed because
	// identity (primary key) columns were not detected.
	ErrMissingIdentity = errors.New("missing identity")

	// ErrDuplicateKey indicates an insert/update violated a unique constraint.
	// Note: many drivers return opaque error types; use IsDuplicateKey to detect.
	ErrDuplicateKey = errors.New("duplicate key")

	// ErrConstraint indicates a generic constraint violation (FK/CK/NOT NULL/etc).
	ErrConstraint = errors.New("constraint violation")
)