supports custom DBTag content

struct.go

@@ -704,6 +704,30 @@ func (s *Struct) valuesWithTags(with, without []string, value interface{}) (valu
 	return
 }
 
+// DBTags returns db tags of s for all exported struct fields.
+func (s *Struct) DBTags() (dbTags []string) {
+	return s.dbTagsWithTags(s.withTags, s.withoutTags)
+}
+
+// DBTagsForTag returns db tags of the s tagged with tag.
+func (s *Struct) DBTagsForTag(tag string) (dbTags []string) {
+	return s.dbTagsWithTags([]string{tag}, nil)
+}
+
+func (s *Struct) dbTagsWithTags(with, without []string) (dbTags []string) {
+	sfs := s.structFieldsParser()
+	tagged := sfs.FilterTags(with, without)
+	if tagged == nil {
+		return
+	}
+
+	dbTags = make([]string, 0, len(tagged.ForRead))
+	for _, sf := range tagged.ForRead {
+		dbTags = append(dbTags, sf.DBTag)
+	}
+	return
+}
+
 func dereferencedType(t reflect.Type) reflect.Type {
 	for k := t.Kind(); k == reflect.Ptr || k == reflect.Interface; k = t.Kind() {
 		t = t.Elem()

struct_test.go

@@ -302,6 +302,13 @@ func TestWithAndWithoutTags(t *testing.T) {
 	a.Equal(structTags.WithoutTag("tag3").WithTag("tag1").WithTag("tag3", "tag2").WithoutTag("tag1", "", "tag3").Columns(), []string{"b"})
 }
 
+func TestStructDBTags(t *testing.T) {
+	a := assert.New(t)
+	a.Equal(userForTest.DBTags(), []string{"id", "", "status", "created_at"})
+	a.Equal(userForTest.DBTagsForTag("important"), []string{"id", "", "status"})
+	a.Equal(userForTest.DBTagsForTag("invalid"), nil)
+}
+
 type State int
 type testDB int
 type testRows int

structfields.go

@@ -28,6 +28,7 @@ type structField struct {
 	As       string
 	Tags     []string
 	IsQuoted bool
+	DBTag    string
 
 	omitEmptyTags omitEmptyTagMap
 }
@@ -95,10 +96,10 @@ func (sfs *structFields) parse(t reflect.Type, mapper FieldMapperFunc, prefix st
 
 		if dbtag == "" {
 			alias = field.Name
+		}
 
-			if mapper != nil {
-				alias = mapper(alias)
-			}
+		if mapper != nil {
+			alias = mapper(alias)
 		}
 
 		// Parse FieldOpt.
@@ -137,6 +138,7 @@ func (sfs *structFields) parse(t reflect.Type, mapper FieldMapperFunc, prefix st
 			As:            fieldas,
 			Tags:          tags,
 			IsQuoted:      isQuoted,
+			DBTag:         dbtag,
 			omitEmptyTags: omitEmptyTags,
 		}