@Override 
  public Integer visitExpr_select(HplsqlParser.Expr_selectContext ctx) {
    if (ctx.select_stmt() != null) {
      stackPush(new Var(evalPop(ctx.select_stmt())));
    }
    else {
      visit(ctx.expr());
    }
    return 0; 
  }
Static SELECT statement (i.e. unquoted) or expression
hplsql/src/main/java/org/apache/hive/hplsql/Exec.java