方法1：
isnull(字段名称,0) as 字段名称
--字符型select isnull(mycol,'0') as newid from mytable--整型select isnull(mycol,0) as newid from mytable方法2：
columnName为字段名
case when columnName is null then 0 else columnName end
例如：
SELECT tt.start_date, tt.start_hour, tt.start_minute, tt.team_num, tt.count, tt.team_num_pk, CASE WHEN tt.countpk IS NULL THEN 0 ELSE tt.countpk END FROM (SELECT start_date, start_hour, start_minute, team_num, (SELECT Sum(count) AS count FROM t_world_cup_guess_transaction_m t WHERE t.team_num = c.team_num AND t.match_num = c.match_num) AS count, team_num_pk, (SELECT Sum(count) AS count FROM t_world_cup_guess_transaction_m t WHERE t.team_num = c.team_num_pk AND t.match_num = c.match_num) AS countpk FROM t_world_cup_guess_competition_process c) tt