diff --git a/.golangci.yml b/.golangci.yml
index a2b7d1b13..709f8b1ad 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -67,4 +67,4 @@ issues:
         - staticcheck
     - path: entc/gen/graph.go
       linters:
-        - gocritic
\ No newline at end of file
+        - gocritic
diff --git a/dialect/sql/schema/schema.go b/dialect/sql/schema/schema.go
index bed17f687..10718b223 100644
--- a/dialect/sql/schema/schema.go
+++ b/dialect/sql/schema/schema.go
@@ -409,9 +409,6 @@ const (
 
 // ConstName returns the constant name of a reference option. It's used by entc for printing the constant name in templates.
 func (r ReferenceOption) ConstName() string {
-	if r == NoAction {
-		return ""
-	}
 	return strings.ReplaceAll(strings.Title(strings.ToLower(string(r))), " ", "")
 }
 
diff --git a/doc/md/schema-edges.md b/doc/md/schema-edges.md
index b5aba0a9e..a667a24ed 100755
--- a/doc/md/schema-edges.md
+++ b/doc/md/schema-edges.md
@@ -1034,6 +1034,12 @@ func (Card) Edges() []ent.Edge {
 
 If the example above, a card entity cannot be created without its owner. 
 
+:::info
+Note that, starting with [v0.10](https://github.com/ent/ent/releases/tag/v0.10.0), foreign key columns are created
+as `NOT NULL` in the database for required edges that are not [self-reference](#o2m-same-type). In order to migrate
+existing foreign key columns, use the [Atlas Migration](migrate.md#atlas-integration) option.
+:::
+
 ## StorageKey
 
 By default, Ent configures edge storage-keys by the edge-owner (the schema that holds the `edge.To`), and not the by
diff --git a/entc/gen/graph.go b/entc/gen/graph.go
index 5a991c335..267ec1ddb 100644
--- a/entc/gen/graph.go
+++ b/entc/gen/graph.go
@@ -456,15 +456,20 @@ func (g *Graph) Tables() (all []*schema.Table, err error) {
 			}
 			switch e.Rel.Type {
 			case O2O, O2M:
-				// The "owner" is the table that owns the relation (we set the foreign-key on)
-				// and "ref" is the referenced table.
+				// The "owner" is the table that owns the relation (we set
+				// the foreign-key on) and "ref" is the referenced table.
 				owner, ref := tables[e.Rel.Table], tables[n.Table()]
 				pk := ref.PrimaryKey[0]
 				column := &schema.Column{Name: e.Rel.Column(), Size: pk.Size, Type: pk.Type, Unique: e.Rel.Type == O2O, SchemaType: pk.SchemaType, Nullable: true}
+				// If it's not a circular reference (self-referencing table),
+				// and the inverse edge is required, make it non-nullable.
+				if n != e.Type && e.Ref != nil && !e.Ref.Optional {
+					column.Nullable = false
+				}
 				mayAddColumn(owner, column)
 				owner.AddForeignKey(&schema.ForeignKey{
 					RefTable:   ref,
-					OnDelete:   deleteAction(e),
+					OnDelete:   deleteAction(e, column),
 					Columns:    []*schema.Column{column},
 					RefColumns: []*schema.Column{ref.PrimaryKey[0]},
 					Symbol:     fkSymbol(e, owner, ref),
@@ -473,10 +478,15 @@ func (g *Graph) Tables() (all []*schema.Table, err error) {
 				ref, owner := tables[e.Type.Table()], tables[e.Rel.Table]
 				pk := ref.PrimaryKey[0]
 				column := &schema.Column{Name: e.Rel.Column(), Size: pk.Size, Type: pk.Type, SchemaType: pk.SchemaType, Nullable: true}
+				// If it's not a circular reference (self-referencing table),
+				// and the edge is non-optional (required), make it non-nullable.
+				if n != e.Type && !e.Optional {
+					column.Nullable = false
+				}
 				mayAddColumn(owner, column)
 				owner.AddForeignKey(&schema.ForeignKey{
 					RefTable:   ref,
-					OnDelete:   deleteAction(e),
+					OnDelete:   deleteAction(e, column),
 					Columns:    []*schema.Column{column},
 					RefColumns: []*schema.Column{ref.PrimaryKey[0]},
 					Symbol:     fkSymbol(e, owner, ref),
@@ -563,8 +573,11 @@ func fkSymbols(e *Edge, c1, c2 *schema.Column) (string, string) {
 }
 
 // deleteAction returns the referential action for DELETE operations of the given edge.
-func deleteAction(e *Edge) schema.ReferenceOption {
-	action := schema.SetNull
+func deleteAction(e *Edge, c *schema.Column) schema.ReferenceOption {
+	action := schema.NoAction
+	if c.Nullable {
+		action = schema.SetNull
+	}
 	if ant := e.EntSQL(); ant != nil && ant.OnDelete != "" {
 		action = schema.ReferenceOption(ant.OnDelete)
 	}
diff --git a/entc/integration/cascadelete/ent/migrate/schema.go b/entc/integration/cascadelete/ent/migrate/schema.go
index 18e8f5419..37e92cb13 100644
--- a/entc/integration/cascadelete/ent/migrate/schema.go
+++ b/entc/integration/cascadelete/ent/migrate/schema.go
@@ -16,7 +16,7 @@ var (
 	CommentsColumns = []*schema.Column{
 		{Name: "id", Type: field.TypeInt, Increment: true},
 		{Name: "text", Type: field.TypeString},
-		{Name: "post_id", Type: field.TypeInt, Nullable: true},
+		{Name: "post_id", Type: field.TypeInt},
 	}
 	// CommentsTable holds the schema information for the "comments" table.
 	CommentsTable = &schema.Table{
diff --git a/entc/integration/edgefield/ent/migrate/schema.go b/entc/integration/edgefield/ent/migrate/schema.go
index 6af5e24d3..6ba6d87d3 100644
--- a/entc/integration/edgefield/ent/migrate/schema.go
+++ b/entc/integration/edgefield/ent/migrate/schema.go
@@ -165,8 +165,8 @@ var (
 	RentalsColumns = []*schema.Column{
 		{Name: "id", Type: field.TypeInt, Increment: true},
 		{Name: "date", Type: field.TypeTime},
-		{Name: "car_id", Type: field.TypeUUID, Nullable: true},
-		{Name: "user_id", Type: field.TypeInt, Nullable: true, SchemaType: map[string]string{"sqlite3": "integer"}},
+		{Name: "car_id", Type: field.TypeUUID},
+		{Name: "user_id", Type: field.TypeInt, SchemaType: map[string]string{"sqlite3": "integer"}},
 	}
 	// RentalsTable holds the schema information for the "rentals" table.
 	RentalsTable = &schema.Table{
@@ -178,13 +178,13 @@ var (
 				Symbol:     "rentals_cars_rentals",
 				Columns:    []*schema.Column{RentalsColumns[2]},
 				RefColumns: []*schema.Column{CarsColumns[0]},
-				OnDelete:   schema.SetNull,
+				OnDelete:   schema.NoAction,
 			},
 			{
 				Symbol:     "rentals_users_rentals",
 				Columns:    []*schema.Column{RentalsColumns[3]},
 				RefColumns: []*schema.Column{UsersColumns[0]},
-				OnDelete:   schema.SetNull,
+				OnDelete:   schema.NoAction,
 			},
 		},
 		Indexes: []*schema.Index{
diff --git a/entc/integration/ent/migrate/schema.go b/entc/integration/ent/migrate/schema.go
index b911a8459..ad47afaaa 100644
--- a/entc/integration/ent/migrate/schema.go
+++ b/entc/integration/ent/migrate/schema.go
@@ -247,7 +247,7 @@ var (
 		{Name: "type", Type: field.TypeString, Nullable: true, Size: 255},
 		{Name: "max_users", Type: field.TypeInt, Nullable: true, Default: 10},
 		{Name: "name", Type: field.TypeString},
-		{Name: "group_info", Type: field.TypeInt, Nullable: true},
+		{Name: "group_info", Type: field.TypeInt},
 	}
 	// GroupsTable holds the schema information for the "groups" table.
 	GroupsTable = &schema.Table{
@@ -259,7 +259,7 @@ var (
 				Symbol:     "groups_group_infos_info",
 				Columns:    []*schema.Column{GroupsColumns[6]},
 				RefColumns: []*schema.Column{GroupInfosColumns[0]},
-				OnDelete:   schema.SetNull,
+				OnDelete:   schema.NoAction,
 			},
 		},
 	}
diff --git a/entc/integration/migrate/entv2/car_create.go b/entc/integration/migrate/entv2/car_create.go
index 4e3bdadee..7f8dc04d5 100644
--- a/entc/integration/migrate/entv2/car_create.go
+++ b/entc/integration/migrate/entv2/car_create.go
@@ -8,6 +8,7 @@ package entv2
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
 	"entgo.io/ent/dialect/sql/sqlgraph"
@@ -29,14 +30,6 @@ func (cc *CarCreate) SetOwnerID(id int) *CarCreate {
 	return cc
 }
 
-// SetNillableOwnerID sets the "owner" edge to the User entity by ID if the given value is not nil.
-func (cc *CarCreate) SetNillableOwnerID(id *int) *CarCreate {
-	if id != nil {
-		cc = cc.SetOwnerID(*id)
-	}
-	return cc
-}
-
 // SetOwner sets the "owner" edge to the User entity.
 func (cc *CarCreate) SetOwner(u *User) *CarCreate {
 	return cc.SetOwnerID(u.ID)
@@ -112,6 +105,9 @@ func (cc *CarCreate) ExecX(ctx context.Context) {
 
 // check runs all checks and user-defined validators on the builder.
 func (cc *CarCreate) check() error {
+	if _, ok := cc.mutation.OwnerID(); !ok {
+		return &ValidationError{Name: "owner", err: errors.New(`entv2: missing required edge "Car.owner"`)}
+	}
 	return nil
 }
 
diff --git a/entc/integration/migrate/entv2/car_update.go b/entc/integration/migrate/entv2/car_update.go
index 56352c9b8..8156e20a7 100644
--- a/entc/integration/migrate/entv2/car_update.go
+++ b/entc/integration/migrate/entv2/car_update.go
@@ -38,14 +38,6 @@ func (cu *CarUpdate) SetOwnerID(id int) *CarUpdate {
 	return cu
 }
 
-// SetNillableOwnerID sets the "owner" edge to the User entity by ID if the given value is not nil.
-func (cu *CarUpdate) SetNillableOwnerID(id *int) *CarUpdate {
-	if id != nil {
-		cu = cu.SetOwnerID(*id)
-	}
-	return cu
-}
-
 // SetOwner sets the "owner" edge to the User entity.
 func (cu *CarUpdate) SetOwner(u *User) *CarUpdate {
 	return cu.SetOwnerID(u.ID)
@@ -69,6 +61,9 @@ func (cu *CarUpdate) Save(ctx context.Context) (int, error) {
 		affected int
 	)
 	if len(cu.hooks) == 0 {
+		if err = cu.check(); err != nil {
+			return 0, err
+		}
 		affected, err = cu.sqlSave(ctx)
 	} else {
 		var mut Mutator = MutateFunc(func(ctx context.Context, m Mutation) (Value, error) {
@@ -76,6 +71,9 @@ func (cu *CarUpdate) Save(ctx context.Context) (int, error) {
 			if !ok {
 				return nil, fmt.Errorf("unexpected mutation type %T", m)
 			}
+			if err = cu.check(); err != nil {
+				return 0, err
+			}
 			cu.mutation = mutation
 			affected, err = cu.sqlSave(ctx)
 			mutation.done = true
@@ -116,6 +114,14 @@ func (cu *CarUpdate) ExecX(ctx context.Context) {
 	}
 }
 
+// check runs all checks and user-defined validators on the builder.
+func (cu *CarUpdate) check() error {
+	if _, ok := cu.mutation.OwnerID(); cu.mutation.OwnerCleared() && !ok {
+		return errors.New(`entv2: clearing a required unique edge "Car.owner"`)
+	}
+	return nil
+}
+
 func (cu *CarUpdate) sqlSave(ctx context.Context) (n int, err error) {
 	_spec := &sqlgraph.UpdateSpec{
 		Node: &sqlgraph.NodeSpec{
@@ -194,14 +200,6 @@ func (cuo *CarUpdateOne) SetOwnerID(id int) *CarUpdateOne {
 	return cuo
 }
 
-// SetNillableOwnerID sets the "owner" edge to the User entity by ID if the given value is not nil.
-func (cuo *CarUpdateOne) SetNillableOwnerID(id *int) *CarUpdateOne {
-	if id != nil {
-		cuo = cuo.SetOwnerID(*id)
-	}
-	return cuo
-}
-
 // SetOwner sets the "owner" edge to the User entity.
 func (cuo *CarUpdateOne) SetOwner(u *User) *CarUpdateOne {
 	return cuo.SetOwnerID(u.ID)
@@ -232,6 +230,9 @@ func (cuo *CarUpdateOne) Save(ctx context.Context) (*Car, error) {
 		node *Car
 	)
 	if len(cuo.hooks) == 0 {
+		if err = cuo.check(); err != nil {
+			return nil, err
+		}
 		node, err = cuo.sqlSave(ctx)
 	} else {
 		var mut Mutator = MutateFunc(func(ctx context.Context, m Mutation) (Value, error) {
@@ -239,6 +240,9 @@ func (cuo *CarUpdateOne) Save(ctx context.Context) (*Car, error) {
 			if !ok {
 				return nil, fmt.Errorf("unexpected mutation type %T", m)
 			}
+			if err = cuo.check(); err != nil {
+				return nil, err
+			}
 			cuo.mutation = mutation
 			node, err = cuo.sqlSave(ctx)
 			mutation.done = true
@@ -279,6 +283,14 @@ func (cuo *CarUpdateOne) ExecX(ctx context.Context) {
 	}
 }
 
+// check runs all checks and user-defined validators on the builder.
+func (cuo *CarUpdateOne) check() error {
+	if _, ok := cuo.mutation.OwnerID(); cuo.mutation.OwnerCleared() && !ok {
+		return errors.New(`entv2: clearing a required unique edge "Car.owner"`)
+	}
+	return nil
+}
+
 func (cuo *CarUpdateOne) sqlSave(ctx context.Context) (_node *Car, err error) {
 	_spec := &sqlgraph.UpdateSpec{
 		Node: &sqlgraph.NodeSpec{
diff --git a/entc/integration/migrate/entv2/migrate/schema.go b/entc/integration/migrate/entv2/migrate/schema.go
index edf198688..ecbae1aa1 100644
--- a/entc/integration/migrate/entv2/migrate/schema.go
+++ b/entc/integration/migrate/entv2/migrate/schema.go
@@ -16,7 +16,7 @@ var (
 	// CarsColumns holds the columns for the "cars" table.
 	CarsColumns = []*schema.Column{
 		{Name: "id", Type: field.TypeInt, Increment: true},
-		{Name: "user_car", Type: field.TypeInt, Nullable: true},
+		{Name: "user_car", Type: field.TypeInt},
 	}
 	// CarsTable holds the schema information for the "cars" table.
 	CarsTable = &schema.Table{
@@ -28,7 +28,7 @@ var (
 				Symbol:     "cars_users_car",
 				Columns:    []*schema.Column{CarsColumns[1]},
 				RefColumns: []*schema.Column{UsersColumns[0]},
-				OnDelete:   schema.SetNull,
+				OnDelete:   schema.NoAction,
 			},
 		},
 	}
diff --git a/entc/integration/migrate/entv2/schema/user.go b/entc/integration/migrate/entv2/schema/user.go
index 0bf5ca2de..073010c2c 100644
--- a/entc/integration/migrate/entv2/schema/user.go
+++ b/entc/integration/migrate/entv2/schema/user.go
@@ -120,7 +120,7 @@ func (User) Indexes() []ent.Index {
 		// this index on MySQL.
 		index.Fields("description").
 			Annotations(entsql.Prefix(100)),
-		// deleting old indexes (name, address),
+		// Deleting old indexes (name, address),
 		// and defining a new one.
 		index.Fields("phone", "age").
 			Unique(),
@@ -135,7 +135,10 @@ func (Car) Edges() []ent.Edge {
 	return []ent.Edge{
 		edge.From("owner", User.Type).
 			Ref("car").
-			Unique(),
+			Unique().
+			// Make a M20 edge from nullable to required.
+			// Requires column and foreign-key migration.
+			Required(),
 	}
 }
 
diff --git a/entc/integration/migrate/migrate_test.go b/entc/integration/migrate/migrate_test.go
index fd7f4122a..a8baea10e 100644
--- a/entc/integration/migrate/migrate_test.go
+++ b/entc/integration/migrate/migrate_test.go
@@ -128,13 +128,14 @@ func TestSQLite(t *testing.T) {
 	)
 
 	SanityV2(t, drv.Dialect(), client)
-	idRange(t, client.Car.Create().SaveX(ctx).ID, 0, 1<<32)
+	u := client.User.Create().SetAge(1).SetName("x").SetNickname("x'").SetPhone("y").SaveX(ctx)
+	idRange(t, client.Car.Create().SetOwner(u).SaveX(ctx).ID, 0, 1<<32)
 	idRange(t, client.Conversion.Create().SaveX(ctx).ID, 1<<32-1, 2<<32)
 	idRange(t, client.CustomType.Create().SaveX(ctx).ID, 2<<32-1, 3<<32)
 	idRange(t, client.Group.Create().SaveX(ctx).ID, 3<<32-1, 4<<32)
 	idRange(t, client.Media.Create().SaveX(ctx).ID, 4<<32-1, 5<<32)
 	idRange(t, client.Pet.Create().SaveX(ctx).ID, 5<<32-1, 6<<32)
-	idRange(t, client.User.Create().SetAge(1).SetName("x").SetNickname("x'").SetPhone("y").SaveX(ctx).ID, 6<<32-1, 7<<32)
+	idRange(t, u.ID, 6<<32-1, 7<<32)
 
 	// Override the default behavior of LIKE in SQLite.
 	// https://www.sqlite.org/pragma.html#pragma_case_sensitive_like
@@ -163,11 +164,12 @@ func V1ToV2(t *testing.T, dialect string, clientv1 *entv1.Client, clientv2 *entv
 	require.NoError(t, clientv2.Schema.Create(ctx, migratev2.WithGlobalUniqueID(true), schema.WithAtlas(true)), "should not create additional resources on multiple runs")
 	SanityV2(t, dialect, clientv2)
 
-	idRange(t, clientv2.Car.Create().SaveX(ctx).ID, 0, 1<<32)
+	u := clientv2.User.Create().SetAge(1).SetName("foo").SetNickname("nick_foo").SetPhone("phone").SaveX(ctx)
+	idRange(t, clientv2.Car.Create().SetOwner(u).SaveX(ctx).ID, 0, 1<<32)
 	idRange(t, clientv2.Conversion.Create().SaveX(ctx).ID, 1<<32-1, 2<<32)
 	// Since "users" created in the migration of v1, it will occupy the range of 1<<32-1 ... 2<<32-1,
 	// even though they are ordered differently in the migration of v2 (groups, pets, users).
-	idRange(t, clientv2.User.Create().SetAge(1).SetName("foo").SetNickname("nick_foo").SetPhone("phone").SaveX(ctx).ID, 3<<32-1, 4<<32)
+	idRange(t, u.ID, 3<<32-1, 4<<32)
 	idRange(t, clientv2.Group.Create().SaveX(ctx).ID, 4<<32-1, 5<<32)
 	idRange(t, clientv2.Media.Create().SaveX(ctx).ID, 5<<32-1, 6<<32)
 	idRange(t, clientv2.Pet.Create().SaveX(ctx).ID, 6<<32-1, 7<<32)
diff --git a/examples/o2o2types/ent/migrate/schema.go b/examples/o2o2types/ent/migrate/schema.go
index 0ee5027b7..cfe135b65 100644
--- a/examples/o2o2types/ent/migrate/schema.go
+++ b/examples/o2o2types/ent/migrate/schema.go
@@ -17,7 +17,7 @@ var (
 		{Name: "id", Type: field.TypeInt, Increment: true},
 		{Name: "expired", Type: field.TypeTime},
 		{Name: "number", Type: field.TypeString},
-		{Name: "user_card", Type: field.TypeInt, Unique: true, Nullable: true},
+		{Name: "user_card", Type: field.TypeInt, Unique: true},
 	}
 	// CardsTable holds the schema information for the "cards" table.
 	CardsTable = &schema.Table{
@@ -29,7 +29,7 @@ var (
 				Symbol:     "cards_users_card",
 				Columns:    []*schema.Column{CardsColumns[3]},
 				RefColumns: []*schema.Column{UsersColumns[0]},
-				OnDelete:   schema.SetNull,
+				OnDelete:   schema.NoAction,
 			},
 		},
 	}
diff --git a/examples/privacytenant/ent/migrate/schema.go b/examples/privacytenant/ent/migrate/schema.go
index a73850330..9b6cfe344 100644
--- a/examples/privacytenant/ent/migrate/schema.go
+++ b/examples/privacytenant/ent/migrate/schema.go
@@ -16,7 +16,7 @@ var (
 	GroupsColumns = []*schema.Column{
 		{Name: "id", Type: field.TypeInt, Increment: true},
 		{Name: "name", Type: field.TypeString, Default: "Unknown"},
-		{Name: "group_tenant", Type: field.TypeInt, Nullable: true},
+		{Name: "group_tenant", Type: field.TypeInt},
 	}
 	// GroupsTable holds the schema information for the "groups" table.
 	GroupsTable = &schema.Table{
@@ -28,7 +28,7 @@ var (
 				Symbol:     "groups_tenants_tenant",
 				Columns:    []*schema.Column{GroupsColumns[2]},
 				RefColumns: []*schema.Column{TenantsColumns[0]},
-				OnDelete:   schema.SetNull,
+				OnDelete:   schema.NoAction,
 			},
 		},
 	}
@@ -48,7 +48,7 @@ var (
 		{Name: "id", Type: field.TypeInt, Increment: true},
 		{Name: "name", Type: field.TypeString, Default: "Unknown"},
 		{Name: "foods", Type: field.TypeJSON, Nullable: true},
-		{Name: "user_tenant", Type: field.TypeInt, Nullable: true},
+		{Name: "user_tenant", Type: field.TypeInt},
 	}
 	// UsersTable holds the schema information for the "users" table.
 	UsersTable = &schema.Table{
@@ -60,7 +60,7 @@ var (
 				Symbol:     "users_tenants_tenant",
 				Columns:    []*schema.Column{UsersColumns[3]},
 				RefColumns: []*schema.Column{TenantsColumns[0]},
-				OnDelete:   schema.SetNull,
+				OnDelete:   schema.NoAction,
 			},
 		},
 	}