游标

    --- mssql    if not cursor_status('global','c_cur')=-3 and not cursor_status('local','c_cur')=-3   -- 存在时候销毁游标                begin                         close c_cur;            deallocate c_cur;                end       declare       c_cur cursor for select id from XXX;      declare @v_id nvarchar(50)      begin          open c_cur;          fetch from c_cur into @v_id;          while @@fetch_status=0              begin                      if cursor_status('global','c_cur')=-3 and cursor_status('local','c_cur')=-3                          begin                                  print '不存在'                          end                      else                          begin                                  print '存在'                          end              fetch from c_cur into @v_ID;        loop:            end;          close c_cur;          deallocate c_cur;      end;            -- oracle 当然可以使用简化的for循环      declare        cursor emp_cur is select * from emp;        empRecord emp%rowtype;      begin        open emp_cur;        loop          fetch emp_cur into empRecord;          exit when emp_cur%notfound;          dbms_output.put_line(empRecord.ename);        end loop;        close emp_cur;      end; -- mysql declare v_d datetime; declare no_more_times integer default 0; -- 定义游标遍历时，作为判断是否遍历完全部记录的标记 declare c_cur cursor for select now(); -- 定义游标 declare continue handler for not found set no_more_times=1; -- 遍历完之后值 open c_cur; repeat    fetch c_cur into v_datetime;    -- if no_more_times<>1 then    loop;    set @s=concat("select now(),'",v_datetime,"';")    prepare s from @s;    execute s; until no_more_times end repeat; -- 结束循环 close c_cur;