added an UpdateColumns helper

database/sql.go

@@ -123,6 +123,9 @@
 
 // SQLUpdate generates a squirrel "update" statement
 // for the given mapped instance (auto-selecting by its pkey)
-func SQLUpdate(m Mapped) squirrel.UpdateBuilder {
+func SQLUpdate(m Mapped, columns ...string) squirrel.UpdateBuilder {
+	if len(columns) == 0 {
+		columns = m.Columns(false)
+	}
 	q := squirrel.
 		Update(m.Table()).
@@ -127,6 +130,6 @@
 	q := squirrel.
 		Update(m.Table()).
-		SetMap(ValuesMap(m, m.Columns(false)...)).Where(
+		SetMap(ValuesMap(m, columns...)).Where(
 		squirrel.Eq{m.PKeyColumn(): m.Values(m.PKeyColumn())})
 	return q
 }

database/sql_helper.go

@@ -128,6 +128,15 @@
 	return nil
 }
 
+// UpdateColumns update a mapped but only for the given columns
+func (h *SQLHelper) UpdateColumns(instance Mapped, columns ...string) error {
+	query := SQLUpdate(instance, columns...)
+	if _, err := h.Exec(query); err != nil {
+		return err
+	}
+	return nil
+}
+
 // UpsertNoPKey upserts a Mapped into the db
 func (h *SQLHelper) UpsertNoPKey(keyCols []string, instances ...Mapped) error {
 	for _, instance := range instances {