diff --git a/ddl/ddl.go b/ddl/ddl.go
index 209abc29b352c..2a1fd8e34ef55 100644
--- a/ddl/ddl.go
+++ b/ddl/ddl.go
@@ -534,6 +534,8 @@ func updateDefaultValue(ctx context.Context, t *tables.Table, col *column.Col) e
 			continue
 		}
 
+		// TODO: check and get timestamp/datetime default value.
+		// refer to getDefaultValue in stmt/stmts/stmt_helper.go.
 		if err0 = t.SetColValue(txn, k, col.DefaultValue); err0 != nil {
 			return errors.Trace(err0)
 		}
diff --git a/ddl/ddl_test.go b/ddl/ddl_test.go
index 95311f44f9295..7343b9674ff35 100644
--- a/ddl/ddl_test.go
+++ b/ddl/ddl_test.go
@@ -23,6 +23,7 @@ import (
 	"github.com/pingcap/tidb/ddl"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/model"
+	mysql "github.com/pingcap/tidb/mysqldef"
 	"github.com/pingcap/tidb/parser"
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/stmt"
@@ -81,20 +82,38 @@ func (ts *testSuite) TestT(c *C) {
 	tb, err := sessionctx.GetDomain(ctx).InfoSchema().TableByName(tbIdent2.Schema, tbIdent2.Name)
 	c.Assert(err, IsNil)
 	c.Assert(tb, NotNil)
-	_, err = tb.AddRecord(ctx, []interface{}{1})
+	rid0, err := tb.AddRecord(ctx, []interface{}{1})
 	c.Assert(err, IsNil)
-	_, err = tb.AddRecord(ctx, []interface{}{2})
+	rid1, err := tb.AddRecord(ctx, []interface{}{2})
 	c.Assert(err, IsNil)
-	alterStmt := statement(`alter table t2 add b enum("bbb") first`).(*stmts.AlterTableStmt)
+	alterStmt := statement(`alter table t2 add b enum("bb") first`).(*stmts.AlterTableStmt)
 	sessionctx.GetDomain(ctx).DDL().AlterTable(ctx, tbIdent2, alterStmt.Specs)
 	c.Assert(alterStmt.Specs[0].String(), Not(Equals), "")
-	_, err = tb.Row(ctx, 1)
+	cols, err := tb.Row(ctx, rid0)
 	c.Assert(err, IsNil)
-	alterStmt = statement("alter table t2 add c timestamp after b").(*stmts.AlterTableStmt)
+	c.Assert(len(cols), Equals, 2)
+	c.Assert(cols[0], Equals, nil)
+	c.Assert(cols[1], Equals, int64(1))
+	alterStmt = statement("alter table t2 add c varchar(255) after b").(*stmts.AlterTableStmt)
 	sessionctx.GetDomain(ctx).DDL().AlterTable(ctx, tbIdent2, alterStmt.Specs)
 	c.Assert(alterStmt.Specs[0].String(), Not(Equals), "")
-	_, err = tb.Row(ctx, 2)
+	tb, err = sessionctx.GetDomain(ctx).InfoSchema().TableByName(tbIdent2.Schema, tbIdent2.Name)
 	c.Assert(err, IsNil)
+	c.Assert(tb, NotNil)
+	cols, err = tb.Row(ctx, rid1)
+	c.Assert(err, IsNil)
+	c.Assert(len(cols), Equals, 3)
+	c.Assert(cols[0], Equals, nil)
+	c.Assert(cols[1], Equals, nil)
+	c.Assert(cols[2], Equals, int64(2))
+	rid3, err := tb.AddRecord(ctx, []interface{}{mysql.Enum{Name: "bb", Value: 1}, "c", 3})
+	c.Assert(err, IsNil)
+	cols, err = tb.Row(ctx, rid3)
+	c.Assert(err, IsNil)
+	c.Assert(len(cols), Equals, 3)
+	c.Assert(cols[0], Equals, mysql.Enum{Name: "bb", Value: 1})
+	c.Assert(cols[1], Equals, "c")
+	c.Assert(cols[2], Equals, int64(3))
 
 	tb, err = sessionctx.GetDomain(ctx).InfoSchema().TableByName(tbIdent.Schema, tbIdent.Name)
 	c.Assert(err, IsNil)
diff --git a/table/tables/tables.go b/table/tables/tables.go
index ee599c17d5dea..c825fe0feba42 100644
--- a/table/tables/tables.go
+++ b/table/tables/tables.go
@@ -39,8 +39,9 @@ import (
 	"github.com/pingcap/tidb/util/errors2"
 )
 
-// KeyLastItem is the last item in key.
-const KeyLastItem = 3
+// The key has tableID, rowID/idx, columnID three parts.
+// keyLastItem is the last item in key.
+const keyLastItem = 3
 
 // Table implements table.Table interface.
 type Table struct {
@@ -138,11 +139,11 @@ func ColumnID(key []byte) (interface{}, error) {
 	if err != nil {
 		return 0, errors.Trace(err)
 	}
-	if len(k) != KeyLastItem {
+	if len(k) != keyLastItem {
 		return 0, errors.New("column not exist")
 	}
 
-	return k[KeyLastItem-1], nil
+	return k[keyLastItem-1], nil
 }
 
 func (t *Table) unflatten(rec interface{}, col *column.Col) (interface{}, error) {
@@ -285,10 +286,10 @@ func (t *Table) setOnUpdateData(ctx context.Context, touched []bool, data []inte
 func (t *Table) SetColValue(txn kv.Transaction, key []byte, data interface{}) error {
 	v, err := t.EncodeValue(data)
 	if err != nil {
-		return err
+		return errors.Trace(err)
 	}
 	if err := txn.Set(key, v); err != nil {
-		return err
+		return errors.Trace(err)
 	}
 	return nil
 }