diff --git a/.golangci.yml b/.golangci.yml
index 3d853d3f..64a4f476 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -14,8 +14,10 @@ linters-settings:
 linters:
   enable-all: true
   disable:
+    - goerr113     # reform v1 should not wrap errors to keep SemVer compatibility
     - gomnd        # too annoying
     - lll          # too annoying
+    - nlreturn     # too annoying
     - testpackage  # too annoying
     - wsl          # too annoying
 
diff --git a/Makefile b/Makefile
index e977bed8..d86177e5 100644
--- a/Makefile
+++ b/Makefile
@@ -20,6 +20,9 @@ env-up-detach:                           ## Start development environment in the
 env-down:                                ## Stop development environment.
 	docker-compose down --volumes --remove-orphans
 
+env-mysql:                               ## Run mysql client.
+	docker exec -ti reform_mysql mysql
+
 test:                                    ## Run all tests and gather coverage.
 	make test-unit
 
diff --git a/base_test.go b/base_test.go
index cc71e45d..a99c642b 100644
--- a/base_test.go
+++ b/base_test.go
@@ -268,11 +268,8 @@ func (s *ReformSuite) TestTimezones() {
 		q := fmt.Sprintf(`INSERT INTO projects (id, name, start) VALUES `+
 			`('11', '11', %s), ('12', '12', %s), ('13', '13', %s), ('14', '14', %s)`,
 			s.q.Placeholder(1), s.q.Placeholder(2), s.q.Placeholder(3), s.q.Placeholder(4))
-
-		withIdentityInsert(s.T(), s.q, "people", func() {
-			_, err := s.q.Exec(q, t1, t2, tVLAT, tHST)
-			s.NoError(err)
-		})
+		_, err := s.q.Exec(q, t1, t2, tVLAT, tHST)
+		s.NoError(err)
 
 		q = `SELECT start, start FROM projects WHERE id IN ('11', '12', '13', '14') ORDER BY id`
 		rows, err := s.q.Query(q)
diff --git a/internal/test/models/good.go b/internal/test/models/good.go
index 6a3efc4d..080cb7f4 100644
--- a/internal/test/models/good.go
+++ b/internal/test/models/good.go
@@ -1,3 +1,4 @@
+//nolint:stylecheck
 package models
 
 import (
@@ -106,17 +107,23 @@ type PersonProject struct {
 	ProjectID string `reform:"project_id"`
 }
 
+// reform:id_only
+type IDOnly struct {
+	ID int32 `reform:"id,pk"`
+}
+
+//reform:constraints
+type Constraints struct {
+	I  int32  `reform:"i"`
+	ID string `reform:"id,pk"`
+}
+
 //reform:legacy.people
 type LegacyPerson struct {
 	ID   int32   `reform:"id,pk"`
 	Name *string `reform:"name"`
 }
 
-// reform:id_only
-type IDOnly struct {
-	ID int32 `reform:"id,pk"`
-}
-
 // check interfaces
 var (
 	_ reform.BeforeInserter = (*Person)(nil)
diff --git a/internal/test/models/good_reform.go b/internal/test/models/good_reform.go
index b4007f3e..54966e75 100644
--- a/internal/test/models/good_reform.go
+++ b/internal/test/models/good_reform.go
@@ -321,102 +321,99 @@ var (
 	_ fmt.Stringer  = (*PersonProject)(nil)
 )
 
-type legacyPersonTableType struct {
+type iDOnlyTableType struct {
 	s parse.StructInfo
 	z []interface{}
 }
 
-// Schema returns a schema name in SQL database ("legacy").
-func (v *legacyPersonTableType) Schema() string {
+// Schema returns a schema name in SQL database ("").
+func (v *iDOnlyTableType) Schema() string {
 	return v.s.SQLSchema
 }
 
-// Name returns a view or table name in SQL database ("people").
-func (v *legacyPersonTableType) Name() string {
+// Name returns a view or table name in SQL database ("id_only").
+func (v *iDOnlyTableType) Name() string {
 	return v.s.SQLName
 }
 
 // Columns returns a new slice of column names for that view or table in SQL database.
-func (v *legacyPersonTableType) Columns() []string {
-	return []string{"id", "name"}
+func (v *iDOnlyTableType) Columns() []string {
+	return []string{"id"}
 }
 
 // NewStruct makes a new struct for that view or table.
-func (v *legacyPersonTableType) NewStruct() reform.Struct {
-	return new(LegacyPerson)
+func (v *iDOnlyTableType) NewStruct() reform.Struct {
+	return new(IDOnly)
 }
 
 // NewRecord makes a new record for that table.
-func (v *legacyPersonTableType) NewRecord() reform.Record {
-	return new(LegacyPerson)
+func (v *iDOnlyTableType) NewRecord() reform.Record {
+	return new(IDOnly)
 }
 
 // PKColumnIndex returns an index of primary key column for that table in SQL database.
-func (v *legacyPersonTableType) PKColumnIndex() uint {
+func (v *iDOnlyTableType) PKColumnIndex() uint {
 	return uint(v.s.PKFieldIndex)
 }
 
-// LegacyPersonTable represents people view or table in SQL database.
-var LegacyPersonTable = &legacyPersonTableType{
-	s: parse.StructInfo{Type: "LegacyPerson", SQLSchema: "legacy", SQLName: "people", Fields: []parse.FieldInfo{{Name: "ID", Type: "int32", Column: "id"}, {Name: "Name", Type: "*string", Column: "name"}}, PKFieldIndex: 0},
-	z: new(LegacyPerson).Values(),
+// IDOnlyTable represents id_only view or table in SQL database.
+var IDOnlyTable = &iDOnlyTableType{
+	s: parse.StructInfo{Type: "IDOnly", SQLSchema: "", SQLName: "id_only", Fields: []parse.FieldInfo{{Name: "ID", Type: "int32", Column: "id"}}, PKFieldIndex: 0},
+	z: new(IDOnly).Values(),
 }
 
 // String returns a string representation of this struct or record.
-func (s LegacyPerson) String() string {
-	res := make([]string, 2)
+func (s IDOnly) String() string {
+	res := make([]string, 1)
 	res[0] = "ID: " + reform.Inspect(s.ID, true)
-	res[1] = "Name: " + reform.Inspect(s.Name, true)
 	return strings.Join(res, ", ")
 }
 
 // Values returns a slice of struct or record field values.
 // Returned interface{} values are never untyped nils.
-func (s *LegacyPerson) Values() []interface{} {
+func (s *IDOnly) Values() []interface{} {
 	return []interface{}{
 		s.ID,
-		s.Name,
 	}
 }
 
 // Pointers returns a slice of pointers to struct or record fields.
 // Returned interface{} values are never untyped nils.
-func (s *LegacyPerson) Pointers() []interface{} {
+func (s *IDOnly) Pointers() []interface{} {
 	return []interface{}{
 		&s.ID,
-		&s.Name,
 	}
 }
 
 // View returns View object for that struct.
-func (s *LegacyPerson) View() reform.View {
-	return LegacyPersonTable
+func (s *IDOnly) View() reform.View {
+	return IDOnlyTable
 }
 
 // Table returns Table object for that record.
-func (s *LegacyPerson) Table() reform.Table {
-	return LegacyPersonTable
+func (s *IDOnly) Table() reform.Table {
+	return IDOnlyTable
 }
 
 // PKValue returns a value of primary key for that record.
 // Returned interface{} value is never untyped nil.
-func (s *LegacyPerson) PKValue() interface{} {
+func (s *IDOnly) PKValue() interface{} {
 	return s.ID
 }
 
 // PKPointer returns a pointer to primary key field for that record.
 // Returned interface{} value is never untyped nil.
-func (s *LegacyPerson) PKPointer() interface{} {
+func (s *IDOnly) PKPointer() interface{} {
 	return &s.ID
 }
 
 // HasPK returns true if record has non-zero primary key set, false otherwise.
-func (s *LegacyPerson) HasPK() bool {
-	return s.ID != LegacyPersonTable.z[LegacyPersonTable.s.PKFieldIndex]
+func (s *IDOnly) HasPK() bool {
+	return s.ID != IDOnlyTable.z[IDOnlyTable.s.PKFieldIndex]
 }
 
 // SetPK sets record primary key.
-func (s *LegacyPerson) SetPK(pk interface{}) {
+func (s *IDOnly) SetPK(pk interface{}) {
 	if i64, ok := pk.(int64); ok {
 		s.ID = int32(i64)
 	} else {
@@ -426,106 +423,221 @@ func (s *LegacyPerson) SetPK(pk interface{}) {
 
 // check interfaces
 var (
-	_ reform.View   = LegacyPersonTable
-	_ reform.Struct = (*LegacyPerson)(nil)
-	_ reform.Table  = LegacyPersonTable
-	_ reform.Record = (*LegacyPerson)(nil)
-	_ fmt.Stringer  = (*LegacyPerson)(nil)
+	_ reform.View   = IDOnlyTable
+	_ reform.Struct = (*IDOnly)(nil)
+	_ reform.Table  = IDOnlyTable
+	_ reform.Record = (*IDOnly)(nil)
+	_ fmt.Stringer  = (*IDOnly)(nil)
 )
 
-type iDOnlyTableType struct {
+type constraintsTableType struct {
 	s parse.StructInfo
 	z []interface{}
 }
 
 // Schema returns a schema name in SQL database ("").
-func (v *iDOnlyTableType) Schema() string {
+func (v *constraintsTableType) Schema() string {
 	return v.s.SQLSchema
 }
 
-// Name returns a view or table name in SQL database ("id_only").
-func (v *iDOnlyTableType) Name() string {
+// Name returns a view or table name in SQL database ("constraints").
+func (v *constraintsTableType) Name() string {
 	return v.s.SQLName
 }
 
 // Columns returns a new slice of column names for that view or table in SQL database.
-func (v *iDOnlyTableType) Columns() []string {
-	return []string{"id"}
+func (v *constraintsTableType) Columns() []string {
+	return []string{"i", "id"}
 }
 
 // NewStruct makes a new struct for that view or table.
-func (v *iDOnlyTableType) NewStruct() reform.Struct {
-	return new(IDOnly)
+func (v *constraintsTableType) NewStruct() reform.Struct {
+	return new(Constraints)
 }
 
 // NewRecord makes a new record for that table.
-func (v *iDOnlyTableType) NewRecord() reform.Record {
-	return new(IDOnly)
+func (v *constraintsTableType) NewRecord() reform.Record {
+	return new(Constraints)
 }
 
 // PKColumnIndex returns an index of primary key column for that table in SQL database.
-func (v *iDOnlyTableType) PKColumnIndex() uint {
+func (v *constraintsTableType) PKColumnIndex() uint {
 	return uint(v.s.PKFieldIndex)
 }
 
-// IDOnlyTable represents id_only view or table in SQL database.
-var IDOnlyTable = &iDOnlyTableType{
-	s: parse.StructInfo{Type: "IDOnly", SQLSchema: "", SQLName: "id_only", Fields: []parse.FieldInfo{{Name: "ID", Type: "int32", Column: "id"}}, PKFieldIndex: 0},
-	z: new(IDOnly).Values(),
+// ConstraintsTable represents constraints view or table in SQL database.
+var ConstraintsTable = &constraintsTableType{
+	s: parse.StructInfo{Type: "Constraints", SQLSchema: "", SQLName: "constraints", Fields: []parse.FieldInfo{{Name: "I", Type: "int32", Column: "i"}, {Name: "ID", Type: "string", Column: "id"}}, PKFieldIndex: 1},
+	z: new(Constraints).Values(),
 }
 
 // String returns a string representation of this struct or record.
-func (s IDOnly) String() string {
-	res := make([]string, 1)
+func (s Constraints) String() string {
+	res := make([]string, 2)
+	res[0] = "I: " + reform.Inspect(s.I, true)
+	res[1] = "ID: " + reform.Inspect(s.ID, true)
+	return strings.Join(res, ", ")
+}
+
+// Values returns a slice of struct or record field values.
+// Returned interface{} values are never untyped nils.
+func (s *Constraints) Values() []interface{} {
+	return []interface{}{
+		s.I,
+		s.ID,
+	}
+}
+
+// Pointers returns a slice of pointers to struct or record fields.
+// Returned interface{} values are never untyped nils.
+func (s *Constraints) Pointers() []interface{} {
+	return []interface{}{
+		&s.I,
+		&s.ID,
+	}
+}
+
+// View returns View object for that struct.
+func (s *Constraints) View() reform.View {
+	return ConstraintsTable
+}
+
+// Table returns Table object for that record.
+func (s *Constraints) Table() reform.Table {
+	return ConstraintsTable
+}
+
+// PKValue returns a value of primary key for that record.
+// Returned interface{} value is never untyped nil.
+func (s *Constraints) PKValue() interface{} {
+	return s.ID
+}
+
+// PKPointer returns a pointer to primary key field for that record.
+// Returned interface{} value is never untyped nil.
+func (s *Constraints) PKPointer() interface{} {
+	return &s.ID
+}
+
+// HasPK returns true if record has non-zero primary key set, false otherwise.
+func (s *Constraints) HasPK() bool {
+	return s.ID != ConstraintsTable.z[ConstraintsTable.s.PKFieldIndex]
+}
+
+// SetPK sets record primary key.
+func (s *Constraints) SetPK(pk interface{}) {
+	if i64, ok := pk.(int64); ok {
+		s.ID = string(i64)
+	} else {
+		s.ID = pk.(string)
+	}
+}
+
+// check interfaces
+var (
+	_ reform.View   = ConstraintsTable
+	_ reform.Struct = (*Constraints)(nil)
+	_ reform.Table  = ConstraintsTable
+	_ reform.Record = (*Constraints)(nil)
+	_ fmt.Stringer  = (*Constraints)(nil)
+)
+
+type legacyPersonTableType struct {
+	s parse.StructInfo
+	z []interface{}
+}
+
+// Schema returns a schema name in SQL database ("legacy").
+func (v *legacyPersonTableType) Schema() string {
+	return v.s.SQLSchema
+}
+
+// Name returns a view or table name in SQL database ("people").
+func (v *legacyPersonTableType) Name() string {
+	return v.s.SQLName
+}
+
+// Columns returns a new slice of column names for that view or table in SQL database.
+func (v *legacyPersonTableType) Columns() []string {
+	return []string{"id", "name"}
+}
+
+// NewStruct makes a new struct for that view or table.
+func (v *legacyPersonTableType) NewStruct() reform.Struct {
+	return new(LegacyPerson)
+}
+
+// NewRecord makes a new record for that table.
+func (v *legacyPersonTableType) NewRecord() reform.Record {
+	return new(LegacyPerson)
+}
+
+// PKColumnIndex returns an index of primary key column for that table in SQL database.
+func (v *legacyPersonTableType) PKColumnIndex() uint {
+	return uint(v.s.PKFieldIndex)
+}
+
+// LegacyPersonTable represents people view or table in SQL database.
+var LegacyPersonTable = &legacyPersonTableType{
+	s: parse.StructInfo{Type: "LegacyPerson", SQLSchema: "legacy", SQLName: "people", Fields: []parse.FieldInfo{{Name: "ID", Type: "int32", Column: "id"}, {Name: "Name", Type: "*string", Column: "name"}}, PKFieldIndex: 0},
+	z: new(LegacyPerson).Values(),
+}
+
+// String returns a string representation of this struct or record.
+func (s LegacyPerson) String() string {
+	res := make([]string, 2)
 	res[0] = "ID: " + reform.Inspect(s.ID, true)
+	res[1] = "Name: " + reform.Inspect(s.Name, true)
 	return strings.Join(res, ", ")
 }
 
 // Values returns a slice of struct or record field values.
 // Returned interface{} values are never untyped nils.
-func (s *IDOnly) Values() []interface{} {
+func (s *LegacyPerson) Values() []interface{} {
 	return []interface{}{
 		s.ID,
+		s.Name,
 	}
 }
 
 // Pointers returns a slice of pointers to struct or record fields.
 // Returned interface{} values are never untyped nils.
-func (s *IDOnly) Pointers() []interface{} {
+func (s *LegacyPerson) Pointers() []interface{} {
 	return []interface{}{
 		&s.ID,
+		&s.Name,
 	}
 }
 
 // View returns View object for that struct.
-func (s *IDOnly) View() reform.View {
-	return IDOnlyTable
+func (s *LegacyPerson) View() reform.View {
+	return LegacyPersonTable
 }
 
 // Table returns Table object for that record.
-func (s *IDOnly) Table() reform.Table {
-	return IDOnlyTable
+func (s *LegacyPerson) Table() reform.Table {
+	return LegacyPersonTable
 }
 
 // PKValue returns a value of primary key for that record.
 // Returned interface{} value is never untyped nil.
-func (s *IDOnly) PKValue() interface{} {
+func (s *LegacyPerson) PKValue() interface{} {
 	return s.ID
 }
 
 // PKPointer returns a pointer to primary key field for that record.
 // Returned interface{} value is never untyped nil.
-func (s *IDOnly) PKPointer() interface{} {
+func (s *LegacyPerson) PKPointer() interface{} {
 	return &s.ID
 }
 
 // HasPK returns true if record has non-zero primary key set, false otherwise.
-func (s *IDOnly) HasPK() bool {
-	return s.ID != IDOnlyTable.z[IDOnlyTable.s.PKFieldIndex]
+func (s *LegacyPerson) HasPK() bool {
+	return s.ID != LegacyPersonTable.z[LegacyPersonTable.s.PKFieldIndex]
 }
 
 // SetPK sets record primary key.
-func (s *IDOnly) SetPK(pk interface{}) {
+func (s *LegacyPerson) SetPK(pk interface{}) {
 	if i64, ok := pk.(int64); ok {
 		s.ID = int32(i64)
 	} else {
@@ -535,17 +647,18 @@ func (s *IDOnly) SetPK(pk interface{}) {
 
 // check interfaces
 var (
-	_ reform.View   = IDOnlyTable
-	_ reform.Struct = (*IDOnly)(nil)
-	_ reform.Table  = IDOnlyTable
-	_ reform.Record = (*IDOnly)(nil)
-	_ fmt.Stringer  = (*IDOnly)(nil)
+	_ reform.View   = LegacyPersonTable
+	_ reform.Struct = (*LegacyPerson)(nil)
+	_ reform.Table  = LegacyPersonTable
+	_ reform.Record = (*LegacyPerson)(nil)
+	_ fmt.Stringer  = (*LegacyPerson)(nil)
 )
 
 func init() {
 	parse.AssertUpToDate(&PersonTable.s, new(Person))
 	parse.AssertUpToDate(&ProjectTable.s, new(Project))
 	parse.AssertUpToDate(&PersonProjectView.s, new(PersonProject))
-	parse.AssertUpToDate(&LegacyPersonTable.s, new(LegacyPerson))
 	parse.AssertUpToDate(&IDOnlyTable.s, new(IDOnly))
+	parse.AssertUpToDate(&ConstraintsTable.s, new(Constraints))
+	parse.AssertUpToDate(&LegacyPersonTable.s, new(LegacyPerson))
 }
diff --git a/parse/parse_test.go b/parse/parse_test.go
index bd510d5a..8346f864 100644
--- a/parse/parse_test.go
+++ b/parse/parse_test.go
@@ -13,6 +13,7 @@ import (
 	. "gopkg.in/reform.v1/parse"
 )
 
+//nolint:gochecknoglobals
 var (
 	person = StructInfo{
 		Type:    "Person",
@@ -50,15 +51,14 @@ var (
 		PKFieldIndex: -1,
 	}
 
-	legacyPerson = StructInfo{
-		Type:      "LegacyPerson",
-		SQLSchema: "legacy",
-		SQLName:   "people",
+	constraints = StructInfo{
+		Type:    "Constraints",
+		SQLName: "constraints",
 		Fields: []FieldInfo{
-			{Name: "ID", Type: "int32", Column: "id"},
-			{Name: "Name", Type: "*string", Column: "name"},
+			{Name: "I", Type: "int32", Column: "i"},
+			{Name: "ID", Type: "string", Column: "id"},
 		},
-		PKFieldIndex: 0,
+		PKFieldIndex: 1,
 	}
 
 	idOnly = StructInfo{
@@ -70,6 +70,17 @@ var (
 		PKFieldIndex: 0,
 	}
 
+	legacyPerson = StructInfo{
+		Type:      "LegacyPerson",
+		SQLSchema: "legacy",
+		SQLName:   "people",
+		Fields: []FieldInfo{
+			{Name: "ID", Type: "int32", Column: "id"},
+			{Name: "Name", Type: "*string", Column: "name"},
+		},
+		PKFieldIndex: 0,
+	}
+
 	extra = StructInfo{
 		Type:    "Extra",
 		SQLName: "extra",
@@ -103,12 +114,13 @@ var (
 func TestFileGood(t *testing.T) {
 	s, err := File(filepath.FromSlash("../internal/test/models/good.go"))
 	assert.NoError(t, err)
-	require.Len(t, s, 5)
+	require.Len(t, s, 6)
 	assert.Equal(t, person, s[0])
 	assert.Equal(t, project, s[1])
 	assert.Equal(t, personProject, s[2])
-	assert.Equal(t, legacyPerson, s[3])
-	assert.Equal(t, idOnly, s[4])
+	assert.Equal(t, idOnly, s[3])
+	assert.Equal(t, constraints, s[4])
+	assert.Equal(t, legacyPerson, s[5])
 }
 
 func TestFileExtra(t *testing.T) {
@@ -156,13 +168,17 @@ func TestObjectGood(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, &personProject, s)
 
-	s, err = Object(new(models.LegacyPerson), "legacy", "people")
-	assert.NoError(t, err)
-	assert.Equal(t, &legacyPerson, s)
-
 	s, err = Object(new(models.IDOnly), "", "id_only")
 	assert.NoError(t, err)
 	assert.Equal(t, &idOnly, s)
+
+	s, err = Object(new(models.Constraints), "", "constraints")
+	assert.NoError(t, err)
+	assert.Equal(t, &constraints, s)
+
+	s, err = Object(new(models.LegacyPerson), "legacy", "people")
+	assert.NoError(t, err)
+	assert.Equal(t, &legacyPerson, s)
 }
 
 func TestObjectExtra(t *testing.T) {
@@ -210,13 +226,17 @@ func TestHelpersGood(t *testing.T) {
 	assert.Equal(t, []string{"person_id", "project_id"}, personProject.Columns())
 	assert.False(t, personProject.IsTable())
 
-	assert.Equal(t, []string{"id", "name"}, legacyPerson.Columns())
-	assert.True(t, legacyPerson.IsTable())
-	assert.Equal(t, FieldInfo{Name: "ID", Type: "int32", Column: "id"}, legacyPerson.PKField())
+	assert.Equal(t, []string{"i", "id"}, constraints.Columns())
+	assert.True(t, constraints.IsTable())
+	assert.Equal(t, FieldInfo{Name: "ID", Type: "string", Column: "id"}, constraints.PKField())
 
 	assert.Equal(t, []string{"id"}, idOnly.Columns())
 	assert.True(t, idOnly.IsTable())
 	assert.Equal(t, FieldInfo{Name: "ID", Type: "int32", Column: "id"}, idOnly.PKField())
+
+	assert.Equal(t, []string{"id", "name"}, legacyPerson.Columns())
+	assert.True(t, legacyPerson.IsTable())
+	assert.Equal(t, FieldInfo{Name: "ID", Type: "int32", Column: "id"}, legacyPerson.PKField())
 }
 
 func TestHelpersExtra(t *testing.T) {
diff --git a/reform-db/cmd_init.go b/reform-db/cmd_init.go
index f843453b..07f623f8 100644
--- a/reform-db/cmd_init.go
+++ b/reform-db/cmd_init.go
@@ -80,7 +80,10 @@ func convertName(sqlName string) string {
 
 // getPrimaryKeyColumn returns single primary key column for given table, or nil.
 func getPrimaryKeyColumn(db *reform.DB, catalog, schema, tableName string) *keyColumnUsage {
-	using := []string{"table_catalog", "table_schema", "table_name"}
+	using := []string{
+		"table_catalog", "table_schema", "table_name",
+		"constraint_catalog", "constraint_schema", "constraint_name",
+	}
 	if db.Dialect == mysql.Dialect {
 		// MySQL doesn't have table_catalog in table_constraints
 		using = using[1:]
@@ -98,22 +101,40 @@ func getPrimaryKeyColumn(db *reform.DB, catalog, schema, tableName string) *keyC
 			ORDER BY ordinal_position DESC`,
 		strings.Join(using, " AND "), db.Placeholder(1), db.Placeholder(2), db.Placeholder(3),
 	)
-	row := db.QueryRow(q, catalog, schema, tableName)
+	rows, err := db.Query(q, catalog, schema, tableName)
+	if err != nil {
+		logger.Fatalf("%s", err)
+	}
+	defer rows.Close() //nolint:errcheck
+
 	var key keyColumnUsage
-	if err := row.Scan(key.Pointers()...); err != nil {
-		if err == reform.ErrNoRows {
-			return nil
+	var count int
+	for {
+		if err = db.NextRow(&key, rows); err != nil {
+			break
 		}
+		count++
+		logger.Debugf("%s", key)
+	}
+	if err != reform.ErrNoRows {
 		logger.Fatalf("%s", err)
 	}
-	if key.OrdinalPosition > 1 {
-		logger.Printf(
-			"Composite primary keys are not supported (found %d columns), skipping it for table %s.",
-			key.OrdinalPosition, tableName,
-		)
+	switch count {
+	case 0:
+		return nil
+	case 1:
+		if key.OrdinalPosition > 1 {
+			logger.Printf(
+				"Composite primary keys are not supported (found %d columns), skipping it for table %s.",
+				key.OrdinalPosition, tableName,
+			)
+			return nil
+		}
+		return &key
+	default:
+		logger.Fatalf("Too many rows found. Please report this bug.")
 		return nil
 	}
-	return &key
 }
 
 // initModelsInformationSchema returns structs from database with information_schema.
diff --git a/reform-db/cmd_init_test.go b/reform-db/cmd_init_test.go
index d9afe0f7..72afadb6 100644
--- a/reform-db/cmd_init_test.go
+++ b/reform-db/cmd_init_test.go
@@ -13,12 +13,13 @@ import (
 func (s *ReformDBSuite) TestInit() {
 	good, err := parse.File("../internal/test/models/good.go")
 	s.Require().NoError(err)
-	s.Require().Len(good, 5)
+	s.Require().Len(good, 6)
 
 	people := good[0]
 	projects := good[1]
 	personProject := good[2]
-	idOnly := good[4]
+	idOnly := good[3]
+	constraints := good[4]
 
 	// patch difference we don't handle
 	people.Type = strings.Replace(people.Type, "Person", "People", -1)
@@ -28,6 +29,7 @@ func (s *ReformDBSuite) TestInit() {
 		people.Fields[1].Type = strings.Replace(people.Fields[1].Type, "int32", "int64", -1)
 		personProject.Fields[0].Type = strings.Replace(personProject.Fields[0].Type, "int32", "int64", -1)
 		idOnly.Fields[0].Type = strings.Replace(idOnly.Fields[0].Type, "int32", "int64", -1)
+		constraints.Fields[0].Type = strings.Replace(constraints.Fields[0].Type, "int32", "int64", -1)
 	}
 
 	dir, err := ioutil.TempDir("", "ReformDBTestInit")
@@ -38,7 +40,7 @@ func (s *ReformDBSuite) TestInit() {
 
 	fis, err := ioutil.ReadDir(dir)
 	s.Require().NoError(err)
-	s.Require().Len(fis, 4)
+	s.Require().Len(fis, 5)
 
 	ff := filepath.Join(dir, "people.go")
 	actual, err := parse.File(ff)
@@ -64,6 +66,12 @@ func (s *ReformDBSuite) TestInit() {
 	s.Require().Len(actual, 1)
 	s.Require().Equal(idOnly, actual[0])
 
+	ff = filepath.Join(dir, "constraints.go")
+	actual, err = parse.File(ff)
+	s.Require().NoError(err)
+	s.Require().Len(actual, 1)
+	s.Require().Equal(constraints, actual[0])
+
 	err = os.RemoveAll(dir)
 	s.Require().NoError(err)
 }
diff --git a/test/sql/mssql_init.sql b/test/sql/mssql_init.sql
index 881e8e1b..0ce917fc 100644
--- a/test/sql/mssql_init.sql
+++ b/test/sql/mssql_init.sql
@@ -24,5 +24,11 @@ CREATE TABLE id_only (
   [id] int identity(1, 1) PRIMARY KEY
 );
 
+CREATE TABLE constraints (
+  [i] int identity(1, 1) NOT NULL,
+  [id] varchar(255) PRIMARY KEY,
+  UNIQUE ([i])
+);
+
 -- to allow insert test data with IDs
 SET IDENTITY_INSERT people ON;
diff --git a/test/sql/mysql_init.sql b/test/sql/mysql_init.sql
index 7f38c77b..b21b73df 100644
--- a/test/sql/mysql_init.sql
+++ b/test/sql/mysql_init.sql
@@ -36,3 +36,10 @@ CREATE TABLE id_only (
   id int NOT NULL AUTO_INCREMENT,
   PRIMARY KEY (id)
 );
+
+CREATE TABLE constraints (
+  i int NOT NULL AUTO_INCREMENT,
+  id varchar(255) NOT NULL,
+  PRIMARY KEY (id),
+  UNIQUE (i)
+);
diff --git a/test/sql/postgres_init.sql b/test/sql/postgres_init.sql
index 8f497101..7e5831c6 100644
--- a/test/sql/postgres_init.sql
+++ b/test/sql/postgres_init.sql
@@ -26,6 +26,12 @@ CREATE TABLE id_only (
   id serial PRIMARY KEY
 );
 
+CREATE TABLE constraints (
+  i serial,
+  id varchar PRIMARY KEY,
+  UNIQUE (i)
+);
+
 CREATE SCHEMA legacy;
 
 CREATE TABLE legacy.people (
diff --git a/test/sql/sqlite3_init.sql b/test/sql/sqlite3_init.sql
index 2b969b09..d876bd05 100644
--- a/test/sql/sqlite3_init.sql
+++ b/test/sql/sqlite3_init.sql
@@ -23,3 +23,9 @@ CREATE TABLE person_project (
 CREATE TABLE id_only (
   id integer NOT NULL PRIMARY KEY AUTOINCREMENT
 );
+
+CREATE TABLE constraints (
+  i integer NOT NULL, -- no AUTOINCREMENT - it works only for PRIMARY KEY: https://www.sqlite.org/autoinc.html
+  id varchar NOT NULL PRIMARY KEY,
+  UNIQUE (i)
+);