Mysql源码学习——打造专属语法(3)

            if (lex->current_select->set_braces(0))

            {

              my_parse_error(ER(ER_SYNTAX_ERROR));

              MYSQL_YYABORT;

            }

            if (sel->linkage == UNION_TYPE &&

                sel->master_unit()->first_select()->braces)

            {

              my_parse_error(ER(ER_SYNTAX_ERROR));

              MYSQL_YYABORT;

            }

          }

          union_clause

        ;

select_part2:

          {

            LEX *lex= Lex;

            SELECT_LEX *sel= lex->current_select;

            if (sel->linkage != UNION_TYPE)

              mysql_init_select(lex);

            lex->current_select->parsing_place= SELECT_LIST;

          }

          select_options select_item_list

          {

            Select->parsing_place= NO_MATTER;

          }

          select_into select_lock_type

        ;

?

select_item_list:

          select_item_list ',' select_item

        | select_item

        | '*'

          {

            THD *thd= YYTHD;

            Item *item= new (thd->mem_root)