diff --git a/manager/database.go b/manager/database.go
index 1550549..404a69d 100644
--- a/manager/database.go
+++ b/manager/database.go
@@ -24,14 +24,14 @@ func boolSetting(source, param string, ok bool) string {
 func timeSetting(source, param string, t time.Duration) string {
 	//make sure 1ms<=t<24h
 	if t < time.Millisecond || t >= 24*time.Hour {
-		return ""
+		return source
 	}
 	return fmt.Sprintf(cDSNFormat, source, param, t)
 }
 
 func stringSetting(source, param, value string) string {
 	if "" == value {
-		return ""
+		return source
 	}
 	return fmt.Sprintf(cDSNFormat, source, param, value)
 }
diff --git a/manager/database_test.go b/manager/database_test.go
index 16a43b9..a1aa9bd 100644
--- a/manager/database_test.go
+++ b/manager/database_test.go
@@ -48,14 +48,16 @@ func TestConcatDSN_Time(t *testing.T) {
 func TestConcatDSN_Time_overflow(t *testing.T) {
 	var setting []Setting
 	ass := assert.New(t)
-	setting = append(setting, SetReadTimeout(time.Microsecond), SetTimeout(24*time.Hour))
-	ass.Equal("", concatDSN(setting), "duration <1ms or >=24h should be invalid")
+	setting = append(setting, SetWriteTimeout(time.Minute), SetReadTimeout(time.Microsecond), SetTimeout(24*time.Hour))
+	ass.Equal("writeTimeout=1m0s", concatDSN(setting), "duration <1ms or >=24h should be invalid")
 }
 
 func TestConcatDSN_String_null(t *testing.T) {
 	var setting []Setting
 	ass := assert.New(t)
-	setting = append(setting, SetCollation(""), SetLoc(""), SetStrict(false), SetInterpolateParams(true))
+	setting = append([]Setting{}, SetCollation(""), SetLoc(""), SetStrict(false), SetInterpolateParams(true))
+	ass.Equal("strict=false&interpolateParams=true", concatDSN(setting), `null value should be ignored`)
+	setting = append([]Setting{}, SetCollation(""), SetStrict(false), SetInterpolateParams(true), SetLoc(""))
 	ass.Equal("strict=false&interpolateParams=true", concatDSN(setting), `null value should be ignored`)
 }