前段時間，一直忙於學習golang語言，沒有時間整理項目中用到的方法，今天趁著有空寫下筆記。

項目中，遇到一個比較"刁鉆"的需求：用戶用Excel導入到系統裏，每一行前面都有一個序號，序號分成兩部分，如下所示：

　　左邊部分是大序號，右邊是小序號，類似於書籍目錄那樣，序號是由用戶自己編寫，而且用戶可以隨意在Excel序號插入任何新序號，用戶不保證新增或者編輯的序號是否正確，我們要做的是檢查這些序號。

以下是我的檢查思路：

1.序號是否連續

　　我們要事先給用戶做一個限制，在大序號後面添加小序號的最大容量是100(其他容量也可以，只不過業務上100夠用了)，即2到2-99都可以，用戶可以隨意追加小序號，例如有序號2，2-1，2-2，3，用戶可以在2-2後面插入2-3。

2.序號有無重復

　　這個比較簡單，SQL裏用group by xx having count(xx) > 1就可以解決，這個放到最後去檢查。

步驟：

0x00

　　導入數據

create table #SerialNum(
    Seq varchar(20)
)
insert into #SerialNum (Seq)
select ‘1‘
union all select ‘1-1‘
union all select ‘1-2‘
union all select ‘1-2‘
union all select ‘1-5‘
union all select ‘1-6‘
union all
 
 select ‘2‘
union all select ‘2-2‘
union all select ‘4‘
union all select ‘6-8‘
union all select ‘6-10‘

0x01

　　寫一個函數，把序號轉換為decimal(18,2)類型的小數，例如把2-1轉換成2.01，因為小序號的容量是100，所以2-1=>2+1/100=2.01。

/*
    select dbo.StringToDecimal(‘2-1‘)    --輸出2.01
    select dbo.StringToDecimal(‘32-68‘)    --輸出32.68
*/
CREATE function
 
 [dbo].[StringToDecimal](
    @Str as varchar(20)
)
returns decimal(18,2)
as
begin
    declare @IntNum decimal(18,2)    --整數部分
    declare @DeNum decimal(18,2)    --小數點後面
    declare @CharIndex int

    set @CharIndex = charindex(‘-‘,@Str)
    IF @CharIndex = 0    --沒有‘-‘直接轉decimal
        return cast(@Str as decimal(18,2))

    set @IntNum = cast(left(@Str,@CharIndex - 1) as decimal(18,2))    --獲取整數部分
    set @DeNum = cast(RIGHT(@Str,len(@Str) - @CharIndex) as decimal(18,2))/100    --獲取小數部分

    return cast(@IntNum + @DeNum as decimal(18,2))
end

　　再把#SerialNum的數據轉換一次，放入另一個臨時表#temp裏。

create table #temp(
    Seq decimal(18,2)
)
insert into #temp (Seq)
select dbo.StringToDecimal(Seq) from #SerialNum

0x02

　　首先找出小序號是否連續，比如1-1，1-2，1-5，1-6，2，這裏就出現斷號，我們要做的是把1-5找出來(但是2前面不算斷號)，提示該序號前面有斷號，先上代碼。

select min(Seq) as Seq    --找出脫離連續序號的一組序號的最小值，就知道哪裏斷開了
    from
        (select [gid] = Seq - cast(cast(pid -1 as decimal(18,2))/100 as decimal(18,2))    --計算差值，如果序號連續，那麽gid一定等於序號的整數部分
                ,Seq
                from 
                    (select row_number() over(partition by cast(Seq as int) order by Seq) as pid    --在每個大序號內的排序
                                                                                ,Seq from #temp) a ) b 
                                                                                    group by cast(Seq as int),gid 
                                                                                    having cast(Seq as int) <> gid    --找出gid不等於序號整數的分組

　　先分解嵌套的a表，SQL中cast(Seq as int)的意圖就是取序號的整數部分，數據如下：

　　再看嵌套的b表，b表的gid就是Seq - (pid)/100，數據如下：

　　看出來了嗎？你會發現當gid等於Seq整數部分的時候就是連續的，不等於就代表出現斷號了，那麽接下來就直接通過group by cast(Seq as int),gid having cast(Seq as int) <> gid把斷號塊找出來，拿出斷號塊的第一個序號，就能準確提醒用戶這裏出現斷號。
0x03

　　接下來檢查出整數序號連續性

select
    min(Seq) as Seq
    from
    (select
        row_number() over (order by _Seq) as pid,Seq
        from
            (select cast(Seq as int) as _Seq, min(Seq) as Seq from #temp group by cast(Seq as int)) a) b group by (cast(Seq as int) - pid) having (cast(Seq as int) - pid) <> 0    --序號減去行號不等於零就是不連續

0x04

　　找出重復的序號

select Seq from #temp group by Seq having count(Seq) > 1

0x05

　　最後把前三步篩選出來的數據用CTE公用表達式整合在一起，放入臨時表#rst

;with t1 as (    --t1篩選出小數序號連續性
    select min(Seq) as Seq    --找出脫離連續序號的一組序號的最小值，就知道哪裏斷開了
        from
            (select [gid] = Seq - cast(cast(pid -1 as decimal(18,2))/100 as decimal(18,2))    --計算差值，如果序號連續，那麽gid一定等於序號的整數部分
                    ,Seq
                    from 
                        (select row_number() over(partition by cast(Seq as int) order by Seq) as pid    --在每個大序號內的排序
                                                                                    ,Seq from #temp) a ) b 
                                                                                        group by cast(Seq as int),gid 
                                                                                        having cast(Seq as int) <> gid    --找出gid不等於序號整數的分組
),t2 as (        --t2篩選出整數序號連續性
    select
        min(Seq) as Seq
        from
        (select
            row_number() over (order by _Seq) as pid,Seq
            from
                (select cast(Seq as int) as _Seq, min(Seq) as Seq from #temp group by cast(Seq as int)) a) b group by (cast(Seq as int) - pid) having (cast(Seq as int) - pid) <> 0    --序號減去行號不等於零就是不連續
),t3 as (        --t3檢查重復性
    select Seq from #temp group by Seq having count(Seq) > 1
    union all
    select Seq from t1
    union all
    select Seq from t2
)
select distinct Seq into #rst from t3 order by Seq

0x06

　　但是要把小數還原成X-XX的格式，所以要寫一個轉換函數。

/*
    select dbo.DecimalToString(2) --輸出2
    select dbo.DecimalToString(2.02)  --輸出2-2
    select dbo.DecimalToString(2.2)  --輸出2-20
*/
CREATE function [dbo].[DecimalToString](
    @Num as decimal(18,2)
)
returns varchar(20)
as
begin
    declare @Index int
    declare @Str varchar(20)

    set @Str = cast(@Num as varchar(20))
    set @Index = charindex(‘.‘,@Str)

    if @Num%1 <> 0
    begin
        set @Str = left(@Str,@Index-1) + ‘-‘ + cast(cast((@Num - cast(@Num as int))*100 as int) as varchar(20))
    end
    else
    begin
        set @Str = cast(cast(@Num as int) as varchar(20))
    end

    return @Str
end

0x07

　　給用戶提示

select N‘序號 ‘ + dbo.DecimalToString(Seq) + N‘ 重復或者前面有斷號‘ as BreakNum from #rst

所有源代碼(可以直接復制按F5運行)：

create table #SerialNum(
    Seq varchar(20)
)
insert into #SerialNum (Seq)
select ‘1‘
union all select ‘1-1‘
union all select ‘1-2‘
union all select ‘1-2‘
union all select ‘1-5‘
union all select ‘1-6‘
union all select ‘2‘
union all select ‘2-2‘
union all select ‘4‘
union all select ‘6-8‘
union all select ‘6-10‘

create table #temp(
    Seq decimal(18,2)
)
insert into #temp (Seq)
select dbo.StringToDecimal(Seq) from #SerialNum

;with t1 as (    --t1篩選出小數序號連續性
    select min(Seq) as Seq    --找出脫離連續序號的一組序號的最小值，就知道哪裏斷開了
        from
            (select [gid] = Seq - cast(cast(pid -1 as decimal(18,2))/100 as decimal(18,2))    --計算差值，如果序號連續，那麽gid一定等於序號的整數部分
                    ,Seq
                    from 
                        (select row_number() over(partition by cast(Seq as int) order by Seq) as pid    --在每個大序號內的排序
                                                                                    ,Seq from #temp) a ) b 
                                                                                        group by cast(Seq as int),gid 
                                                                                        having cast(Seq as int) <> gid    --找出gid不等於序號整數的分組
),t2 as (        --t2篩選出整數序號連續性
    select
        min(Seq) as Seq
        from
        (select
            row_number() over (order by _Seq) as pid,Seq
            from
                (select cast(Seq as int) as _Seq, min(Seq) as Seq from #temp group by cast(Seq as int)) a) b group by (cast(Seq as int) - pid) having (cast(Seq as int) - pid) <> 0    --序號減去行號不等於零就是不連續
),t3 as (        --t3檢查重復性
    select Seq from #temp group by Seq having count(Seq) > 1
    union all
    select Seq from t1
    union all
    select Seq from t2
)
select distinct Seq into #rst from t3 order by Seq


select N‘序號 ‘ + dbo.DecimalToString(Seq) + N‘ 重復或者前面有斷號‘ as BreakNum from #rst

drop table #SerialNum
drop table #temp
drop table #rst

總結：這是本人第一次寫博客筆記，語言組織上可能有一點缺陷，望前輩們見諒。

PS：此文章是原創，轉載需聲明出處。

現實項目中用戶隨意添加序號，如何用SQL解決序號連續性問題