查詢某條數據的上一條和下一條數據的Sql語句

searchNum：為當前查詢的編號

1.查詢上一條數據

select * from tbl_stu where num = (select max(num) from tbl_stu where num < searchNum)

2.查詢下一條數據

select * from tbl_stu where num = (select min(num) from tbl_stu where num > searchNum)

3.查詢上一條和下一條數據

select * from tbl_stu 
where num in(
  (select max(num) from tbl_stu where num < searchNum), 
  (select min(num) from tbl_stu where num > searchNum)
)