diff --git a/dialect.go b/dialect.go
index de72b79a..e879588b 100644
--- a/dialect.go
+++ b/dialect.go
@@ -14,7 +14,7 @@ type Dialect interface {
 	GetName() string
 
 	// SetDB set db for dialect
-	SetDB(db *sql.DB)
+	SetDB(db SQLCommon)
 
 	// BindVar return the placeholder for actual values in SQL statements, in many dbs it is "?", Postgres using $1
 	BindVar(i int) string
@@ -50,7 +50,7 @@ type Dialect interface {
 
 var dialectsMap = map[string]Dialect{}
 
-func newDialect(name string, db *sql.DB) Dialect {
+func newDialect(name string, db SQLCommon) Dialect {
 	if value, ok := dialectsMap[name]; ok {
 		dialect := reflect.New(reflect.TypeOf(value).Elem()).Interface().(Dialect)
 		dialect.SetDB(db)
diff --git a/dialect_common.go b/dialect_common.go
index 601afd4c..1554151c 100644
--- a/dialect_common.go
+++ b/dialect_common.go
@@ -1,7 +1,6 @@
 package gorm
 
 import (
-	"database/sql"
 	"fmt"
 	"reflect"
 	"regexp"
@@ -15,7 +14,7 @@ type DefaultForeignKeyNamer struct {
 }
 
 type commonDialect struct {
-	db *sql.DB
+	db SQLCommon
 	DefaultForeignKeyNamer
 }
 
@@ -27,7 +26,7 @@ func (commonDialect) GetName() string {
 	return "common"
 }
 
-func (s *commonDialect) SetDB(db *sql.DB) {
+func (s *commonDialect) SetDB(db SQLCommon) {
 	s.db = db
 }
 
diff --git a/dialects/mssql/mssql.go b/dialects/mssql/mssql.go
index 7c685c9f..c3c81aa2 100644
--- a/dialects/mssql/mssql.go
+++ b/dialects/mssql/mssql.go
@@ -1,7 +1,6 @@
 package mssql
 
 import (
-	"database/sql"
 	"fmt"
 	"reflect"
 	"strconv"
@@ -24,7 +23,7 @@ func init() {
 }
 
 type mssql struct {
-	db *sql.DB
+	db gorm.SQLCommon
 	gorm.DefaultForeignKeyNamer
 }
 
@@ -32,7 +31,7 @@ func (mssql) GetName() string {
 	return "mssql"
 }
 
-func (s *mssql) SetDB(db *sql.DB) {
+func (s *mssql) SetDB(db gorm.SQLCommon) {
 	s.db = db
 }
 
diff --git a/interface.go b/interface.go
index 7b02aa66..55128f7f 100644
--- a/interface.go
+++ b/interface.go
@@ -2,7 +2,8 @@ package gorm
 
 import "database/sql"
 
-type sqlCommon interface {
+// SQLCommon is the minimal database connection functionality gorm requires.  Implemented by *sql.DB.
+type SQLCommon interface {
 	Exec(query string, args ...interface{}) (sql.Result, error)
 	Prepare(query string) (*sql.Stmt, error)
 	Query(query string, args ...interface{}) (*sql.Rows, error)
diff --git a/main.go b/main.go
index 9ea10909..9ae560a1 100644
--- a/main.go
+++ b/main.go
@@ -16,7 +16,7 @@ type DB struct {
 	RowsAffected int64
 
 	// single db
-	db                sqlCommon
+	db                SQLCommon
 	blockGlobalUpdate bool
 	logMode           int
 	logger            logger
@@ -47,7 +47,7 @@ func Open(dialect string, args ...interface{}) (db *DB, err error) {
 		return nil, err
 	}
 	var source string
-	var dbSQL *sql.DB
+	var dbSQL SQLCommon
 
 	switch value := args[0].(type) {
 	case string:
@@ -59,8 +59,7 @@ func Open(dialect string, args ...interface{}) (db *DB, err error) {
 			source = args[1].(string)
 		}
 		dbSQL, err = sql.Open(driver, source)
-	case *sql.DB:
-		source = reflect.Indirect(reflect.ValueOf(value)).FieldByName("dsn").String()
+	case SQLCommon:
 		dbSQL = value
 	}
 
@@ -90,21 +89,27 @@ func (s *DB) New() *DB {
 	return clone
 }
 
-// Close close current db connection
+type closer interface {
+	Close() error
+}
+
+// Close close current db connection.  If database connection is not an io.Closer, returns an error.
 func (s *DB) Close() error {
-	if db, ok := s.parent.db.(*sql.DB); ok {
+	if db, ok := s.parent.db.(closer); ok {
 		return db.Close()
 	}
 	return errors.New("can't close current db")
 }
 
 // DB get `*sql.DB` from current connection
+// If the underlying database connection is not a *sql.DB, returns nil
 func (s *DB) DB() *sql.DB {
-	return s.db.(*sql.DB)
+	db, _ := s.db.(*sql.DB)
+	return db
 }
 
 // CommonDB return the underlying `*sql.DB` or `*sql.Tx` instance, mainly intended to allow coexistence with legacy non-GORM code.
-func (s *DB) CommonDB() sqlCommon {
+func (s *DB) CommonDB() SQLCommon {
 	return s.db
 }
 
@@ -449,7 +454,7 @@ func (s *DB) Begin() *DB {
 	c := s.clone()
 	if db, ok := c.db.(sqlDb); ok {
 		tx, err := db.Begin()
-		c.db = interface{}(tx).(sqlCommon)
+		c.db = interface{}(tx).(SQLCommon)
 		c.AddError(err)
 	} else {
 		c.AddError(ErrCantStartTransaction)
diff --git a/scope.go b/scope.go
index 45f7185f..86fd1d42 100644
--- a/scope.go
+++ b/scope.go
@@ -58,7 +58,7 @@ func (scope *Scope) NewDB() *DB {
 }
 
 // SQLDB return *sql.DB
-func (scope *Scope) SQLDB() sqlCommon {
+func (scope *Scope) SQLDB() SQLCommon {
 	return scope.db.db
 }
 
@@ -391,7 +391,7 @@ func (scope *Scope) InstanceGet(name string) (interface{}, bool) {
 func (scope *Scope) Begin() *Scope {
 	if db, ok := scope.SQLDB().(sqlDb); ok {
 		if tx, err := db.Begin(); err == nil {
-			scope.db.db = interface{}(tx).(sqlCommon)
+			scope.db.db = interface{}(tx).(SQLCommon)
 			scope.InstanceSet("gorm:started_transaction", true)
 		}
 	}