Fix update with Alias (go-xorm#1455)

Author: lunny

session_update.go

@@ -377,10 +377,23 @@ func (session *Session) Update(bean interface{}, condiBean ...interface{}) (int6
 		return 0, errors.New("No content found to be updated")
 	}
 
-	sqlStr = fmt.Sprintf("UPDATE %v%v SET %v %v",
+	var tableAlias = session.engine.Quote(tableName)
+	var fromSQL string
+	if session.statement.TableAlias != "" {
+		switch session.engine.dialect.DBType() {
+		case core.MSSQL:
+			fromSQL = fmt.Sprintf("FROM %s %s ", tableAlias, session.statement.TableAlias)
+			tableAlias = session.statement.TableAlias
+		default:
+			tableAlias = fmt.Sprintf("%s AS %s", tableAlias, session.statement.TableAlias)
+		}
+	}
+
+	sqlStr = fmt.Sprintf("UPDATE %v%v SET %v %v%v",
 		top,
-		session.engine.Quote(tableName),
+		tableAlias,
 		strings.Join(colNames, ", "),
+		fromSQL,
 		condSQL)
 
 	res, err := session.exec(sqlStr, append(args, condArgs...)...)

session_update_test.go

@@ -1328,3 +1328,34 @@ func TestUpdateExprs(t *testing.T) {
 	assert.EqualValues(t, 2, ue.NumIssues)
 	assert.EqualValues(t, "lunny xiao", ue.Name)
 }
+
+func TestUpdateAlias(t *testing.T) {
+	assert.NoError(t, prepareEngine())
+
+	type UpdateAlias struct {
+		Id        int64
+		NumIssues int
+		Name      string
+	}
+
+	assertSync(t, new(UpdateAlias))
+
+	_, err := testEngine.Insert(&UpdateAlias{
+		NumIssues: 1,
+		Name:      "lunny",
+	})
+	assert.NoError(t, err)
+
+	_, err = testEngine.Alias("ua").Where("ua.id = ?", 1).Update(&UpdateAlias{
+		NumIssues: 2,
+		Name:      "lunny xiao",
+	})
+	assert.NoError(t, err)
+
+	var ue UpdateAlias
+	has, err := testEngine.Get(&ue)
+	assert.NoError(t, err)
+	assert.True(t, has)
+	assert.EqualValues(t, 2, ue.NumIssues)
+	assert.EqualValues(t, "lunny xiao", ue.Name)
+}