docs: protected SqlSelect createSourceSelectForUpdate(SqlUpdate call) {
  		final SqlNodeList selectList = new SqlNodeList(SqlParserPos.ZERO);
  		selectList.add(SqlIdentifier.star(SqlParserPos.ZERO));
  		int ordinal = 0;
  		for (SqlNode exp : call.getSourceExpressionList()) {
  			// Force unique aliases to avoid a duplicate for Y with
  			// SET X=Y
  			String alias = SqlUtil.deriveAliasFromOrdinal(ordinal);
  			selectList.add(SqlValidatorUtil.addAlias(exp, alias));
  			++ordinal;
  		}
  		SqlNode sourceTable = call.getTargetTable();
  		if (call.getAlias() != null) {
  			sourceTable =
  				SqlValidatorUtil.addAlias(
  					sourceTable,
  					call.getAlias().getSimple());
  		}
  		return new SqlSelect(SqlParserPos.ZERO, null, selectList, sourceTable,
  			call.getCondition(), null, null, null, null, null, null);
  	}