Question

我正在SQL Server 2016 SP1中开发存储过程。

此语句返回重复的值。它将相同的值重复四次：

Select Serial = 
    CASE al.NumberEncoding
        WHEN 3 THEN RIGHT(ex.Serial,LEN(ex.Serial)-2) 
        ELSE RIGHT(ex.Serial,LEN(ex.Serial)-18)       
    END, AggregationLevel
from ExternalCode ex, AggregationLevelConfiguration al
where ex.ProductionOrderId = 4 and 
        ex.AggregationLevel = al.AggregationLevelConfigurationId

我得到这样的东西：

Serial   AggregationLevel
RP4X6BXC1N0RG7  1
RP4X6BXC1N0RG7  1
RP4X6BXC1N0RG7  1
RP4X6BXC1N0RG7  1
RP4X6BXC1N0RG7  1
P5KNX3KBT4997Z  1
P5KNX3KBT4997Z  1
P5KNX3KBT4997Z  1
P5KNX3KBT4997Z  1
P5KNX3KBT4997Z  1
A6GZ9E8ZFA8YMV  1
A6GZ9E8ZFA8YMV  1
A6GZ9E8ZFA8YMV  1
A6GZ9E8ZFA8YMV  1
A6GZ9E8ZFA8YMV  1
EMAMKM4356DHGV  1
EMAMKM4356DHGV  1
EMAMKM4356DHGV  1
EMAMKM4356DHGV  1
EMAMKM4356DHGV  1
WASBFP0EYDM7BM  1
WASBFP0EYDM7BM  1
WASBFP0EYDM7BM  1
WASBFP0EYDM7BM  1
WASBFP0EYDM7BM  1

有什么办法可以避免这种重复？

Answer 1

添加GROUP BY来删除重复项：

SELECT Serial, AggregationLevel
FROM (
    SELECT
        CASE al.NumberEncoding
            WHEN 3 THEN RIGHT(ex.Serial,LEN(ex.Serial)-2) 
            ELSE RIGHT(ex.Serial,LEN(ex.Serial)-18)       
        END as Serial
    ,   AggregationLevel
    FROM ExternalCode ex
    JOIN AggregationLevelConfiguration al ON ex.AggregationLevel = al.AggregationLevelConfigurationId
    WHERE ex.ProductionOrderId = 4
) nested
GROUP BY Serial, AggregationLevel

Answer 2

我只会使用DISTINCT而不是subquery：

select distinct (case when al.NumberEncoding = 3 
                      then RIGHT(ex.Serial,LEN(ex.Serial)-2) 
                      else RIGHT(ex.Serial,LEN(ex.Serial)-18)       
                  end) as Serial, AggregationLevel
from ExternalCode ex inner join 
     AggregationLevelConfiguration al
     on ex.AggregationLevel = al.AggregationLevelConfigurationId
where ex.ProductionOrderId = 4;

Answer 3

尝试一下

       SELECT * FROM
        (
        SELECT *, ROW_NUMBER()OVER(PARTITION BY Serial ORDER BY Serial) AS Dup
        FROM
        (
        Select Serial = CASE al.NumberEncoding
                        WHEN 3 THEN RIGHT(ex.Serial,LEN(ex.Serial)-2) 
                        ELSE RIGHT(ex.Serial,LEN(ex.Serial)-18)       
                        END AS AggregationLevel
        FROM ExternalCode ex, AggregationLevelConfiguration al
        where ex.ProductionOrderId = 4 and 
        ex.AggregationLevel = al.AggregationLevelConfigurationId
        )dt
        )Fnl WHERE Dup=1

Answer 4

我找到了解决方法：

SELECT Serial, AggregationLevel
FROM (
    SELECT
        CASE al.NumberEncoding
            WHEN 3 THEN RIGHT(ex.Serial,LEN(ex.Serial)-2) 
            ELSE RIGHT(ex.Serial,LEN(ex.Serial)-18)       
        END as Serial
    ,   AggregationLevel
    FROM ExternalCode ex
    JOIN AggregationLevelConfiguration al ON ex.AggregationLevel = al.AggregationLevelConfigurationId
    WHERE ex.ProductionOrderId = 4 and al.ProductionOrderId = 4
) nested

我还使用AggregationLevelConfiguration和ProductionOrderId添加了约束，而没有使用Group by。

select返回相同值四次

4 个答案: