command.setTableName(tableName);
command.setComment(readCommentIf());
if (readIf("(")) {
if (!readIf(")")) {
do {
DefineCommand c = parseAlterTableAddConstraintIf(tableName, schema);
if (c != null) {
command.addConstraintCommand(c);
} else {
String columnName = readColumnIdentifier();
Column column = parseColumnForTable(columnName, true);