1.需求
求出缺失範圍
2.示例
根據表中某個變化字段，求出變化欄位的缺失範圍。如下給出乙個例子：
下面是乙個表x，其中的資料如下：
mysql> select * from x;
+------+
| a |
+------+
| 3 |
| 4 |
| 5 |
| 6 |
| 100 |
| 101 |
| 102 |
| 105 |
| 106 |
| 107 |
+------+
10 rows in set (0.03 sec)
3.**一
select a
from x as x1
where not exists
( select *
from x as x2
where x1.a + 1 = x2.a
);
+------+
| a |
+------+
| 6 |
| 102 |
| 107 |
+------+
3 rows in set (0.00 sec)
select a+1 as start_range
from x as x1
where not exists
( select *
from x as x2
where x1.a + 1 = x2.a
)and a< (select max(a) from x);
+-------------+
| start_range |
+-------------+
| 7 |
| 103 |
+-------------+
2 rows in set (0.00 sec)
select
a+1 as start_range
,( select
min(a) -1
from x as x3
where x3.a > x1.a
) as end_range
from x as x1
where not exists
( select a
from x as x2
where x1.a + 1 = x2.a
)and a< (select max(a) from x);
+-------------+-----------+
| start_range | end_range |
+-------------+-----------+
| 7 | 99 |
| 103 | 104 |
+-------------+-----------+
2 rows in set (0.00 sec)
select a as cur,
( select
min(a)
from x as x1
where x1.a > x2.a
) as next
from x as x2;
+------+------+
| cur | next |
+------+------+
| 3 | 4 |
| 4 | 5 |
| 5 | 6 |
| 6 | 100 |
| 100 | 101 |
| 101 | 102 |
| 102 | 105 |
| 105 | 106 |
| 106 | 107 |
| 107 | null |
+------+------+
10 rows in set (0.00 sec)
select
cur+1 as start_range,
next-1 as end_range
from
( select
a as cur,
(select min(a) from x as x2
where x2.a > x1.a)as next
from x as x1
)as x3
where next - cur > 1
+-------------+-----------+
| start_range | end_range |
+-------------+-----------+
| 7 | 99 |
| 103 | 104 |
+-------------+-----------+
2 rows in set (0.01 sec)
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