Method set_linkage

sql/sql_lex.h:707–713

                                          st_select_lex_node *end_chain_node);
  void move_as_slave(st_select_lex_node *new_master);
  void set_linkage(enum sub_select_type l)
  {
    DBUG_ENTER("st_select_lex_node::set_linkage");
    DBUG_PRINT("info", ("node: %p  linkage: %d->%d", this, linkage, l));
    linkage= l;
    DBUG_VOID_RETURN;
  }
  /*
    This method created for reiniting LEX in mysql_admin_table() and can be
    used only if you are going remove all SELECT_LEX & units except belonger