序列号自动生成

Question

自动生成序列号时遇到问题。

如何正确使用 row_number() 或是否有其他方法可以达到预期的效果？

注：我想写查询不使用CASE。

SELECT 
 row_number() over (order by COALESCE(legs.sta, legs.eta) ASC) sno,
 legs.Flight_ID flightId,
 legs.flight,
 legs.flightDate           
FROM Flt_OperativeFlight_Legs LEG
ORDER BY COALESCE(legs.sta, legs.eta) ASC

当前结果：

+------+--------+-------------------------+
| sno  | flight |       flightDate        |
+------+--------+-------------------------+
|    1 | 3K0722 | 2019-01-08 17:10:00.000 |
|    2 | 3K0722 | 2019-01-08 20:20:00.000 |
|    3 | 3K0723 | 2019-01-09 17:10:00.000 |
|    4 | 3K0724 | 2019-01-10 20:20:00.000 |
+------+--------+-------------------------+

预期结果：

+------+--------+-------------------------+
| sno  | flight |       flightDate        |
+------+--------+-------------------------+
|    1 | 3K0722 | 2019-01-08 17:10:00.000 |
|      |        | 2019-01-08 20:20:00.000 |
|    2 | 3K0723 | 2019-01-09 17:10:00.000 |
|    3 | 3K0724 | 2019-01-10 20:20:00.000 |
+------+--------+-------------------------+

Answer 1

您可以使用 DENSE_RANK 而不是 ROW_NUMBER

SELECT 
 DENSE_RANK() over (order by COALESCE(legs.sta, legs.eta, legs.ata) ASC) as "s.no",
 legs.Flight_ID flightId
 ,legs.flight
 ,legs.flightDate
FROM Flt_OperativeFlight_Legs LEG
ORDER BY COALESCE(legs.sta, legs.eta, legs.ata) ASC

Answer 2

您需要其他 row_number() :

SELECT DENSE_RANK() OVER (ORDER BY flt_id, flight) AS Sr,
       (CASE WHEN Seq = 1 
             THEN flightId
        END) AS Flight_ID,
       (CASE WHEN Seq = 1 
             THEN flight
        END) AS flight, flightDate
FROM (SELECT ROW_NUMBER() OVER(PARTITION BY Flight_ID, flight ORDER BY flightDate) AS Seq,
             legs.Flight_ID flightId, legs.flight, legs.flightDate
      FROM Flt_OperativeFlight_Legs LEG
     ) l;

Answer 3

您可以尝试在子查询中使用 ROW_NUMBER window 函数，然后使用 DENSE_RANK window 函数创建 no 列 CASE WHEN 表达式得到 rn = 1 行。

SELECT (CASE WHEN rn = 1 THEN DENSE_RANK() over(order by flight) END) no,
       (CASE WHEN rn = 1 THEN flt_id END) flt_id,
       (CASE WHEN rn = 1 THEN flight END) flight,
       flightDate
FROM 
(
    SELECT *,ROW_NUMBER() OVER(PARTITION BY flt_id,flight ORDER BY flightDate) rn
    FROM Flt_OperativeFlight_Legs 
) t1

sqlfiddle

Answer 4

请参考以下解决方案，清空重复数据我需要使用CASE表达式

在 CTE 表达式中，我将 Row_Number 和 Dense_Rank 函数与 Partition By clause

结合使用

;with cte as (
    select
        ROW_NUMBER() over (order by flight, flightDate) as num,
        DENSE_RANK() over (order by flight) as [no],
        ROW_NUMBER() over (partition by flight order by flightDate) as rn,
        flight,
        flightDate
    from Flt_OperativeFlight_Legs legs
)
select
    case when rn > 1 then null else [no] end as [no],
    case when rn > 1 then null else flight end as flight,
    flightDate
from cte
order by num

输出如下

序列号自动生成

Serial number auto generation

sql

tsql

sql-server

group-by

rowcount