Microsoft SQL Server：每天生成一个序列号

Question

我的任务是为项目每天创建一个递增的序列号。多个进程（理论上在多台机器上）需要产生这个。由于我在这个项目中使用的SQL Server（2008）反正它结束了作为

[date]_[number] 

像

20101215_00000001 
20101215_00000002 
... 
20101216_00000001 
20101216_00000002 
... 

，我试图用T-SQL/SQL魔术做到这一点。这就是我现在：

我创建了一个包含这样的序号表：

CREATE TABLE [dbo].[SequenceTable](
    [SequenceId] [bigint] IDENTITY(1,1) NOT NULL, 
    [SequenceDate] [date] NOT NULL, 
    [SequenceNumber] [int] NULL 
) ON [PRIMARY] 

我天真的解决方案至今被触发，插入后，即设置的SequenceNumber：

CREATE TRIGGER [dbo].[GenerateMessageId] 
ON [dbo].[SequenceTable] 
AFTER INSERT 
AS 
BEGIN 
-- SET NOCOUNT ON added to prevent extra result sets from 
-- interfering with SELECT statements. 
SET NOCOUNT ON; 

-- The ID of the record we just inserted 
DECLARE @InsertedId bigint; 
SET @InsertedId = (SELECT SequenceId FROM Inserted) 

-- The next SequenceNumber that we're adding to the new record 
DECLARE @SequenceNumber int; 
SET @SequenceNumber = (
    SELECT SequenceNumber FROM 
    (
     SELECT SequenceId, ROW_NUMBER() OVER(PARTITION BY SequenceDate ORDER BY SequenceDate ASC) AS SequenceNumber 
     FROM SequenceTable 
    ) tmp 
    WHERE SequenceId = @InsertedId 
) 

-- Update the record and set the SequenceNumber 
UPDATE 
    SequenceTable 
SET 
    SequenceTable.SequenceNumber = ''+@SequenceNumber 
FROM 
    SequenceTable 
INNER JOIN 
    inserted ON SequenceTable.SequenceId = inserted.SequenceId 
END 

正如我所说的那样，这太天真了，并且为一个单独的数字保留了整整一天的行数，我不再需要：我做一个插入，获取生成的序列号，然后忽略表。没有必要商店他们在我身边，我只需要生成一次。另外，我很确定这不会很好地扩展，表中包含的行越多，越慢（即我不想陷入“在我的开发机器上只有10.000行的陷阱”）。

我想现在的方式更多的是用一些创造力来看待SQL，但结果似乎是 - erm - 没那么有用。更聪明的想法？

Answer 1

忘掉那SequenceTable。您应该在决赛桌上创建两列：日期时间和身份。如果您真的需要将它们组合起来，只需添加一个计算列即可。

我想这将是类似的东西：

CREATE TABLE [dbo].[SomeTable] (
    [SequenceId] [bigint] IDENTITY(1,1) NOT NULL, 
    [SequenceDate] [date] NOT NULL, 
    [SequenceNumber] AS (CAST(SequenceDate AS VARCHAR(10)) + '_' + RIGHT('0000000000' + CAST(SequenceID AS VARCHAR(10)), 10)) PERSISTED 
) ON [PRIMARY] 

这样将扩大 - 你没有创建任何形式的中介或临时数据。

编辑我仍然认为上面的答案是最好的解决方案。但还有另一种选择：计算列可以参考函数...

所以做到这一点：

CREATE FUNCTION dbo.GetNextSequence (
    @sequenceDate DATE, 
    @sequenceId BIGINT 
) RETURNS VARCHAR(17) 
AS 
BEGIN 
    DECLARE @date VARCHAR(8) 
    SET @date = CONVERT(VARCHAR, @sequenceDate, 112) 

    DECLARE @number BIGINT 
    SELECT 
     @number = COALESCE(MAX(aux.SequenceId) - MIN(aux.SequenceId) + 2, 1) 
    FROM 
     SomeTable aux 
    WHERE 
     aux.SequenceDate = @sequenceDate 
     AND aux.SequenceId < @sequenceId 

    DECLARE @result VARCHAR(17) 
    SET @result = @date + '_' + RIGHT('00000000' + CAST(@number AS VARCHAR(8)), 8) 
    RETURN @result 
END 
GO 

CREATE TABLE [dbo].[SomeTable] (
    [SequenceId] [bigint] IDENTITY(1,1) NOT NULL, 
    [SequenceDate] [date] NOT NULL, 
    [SequenceNumber] AS (dbo.GetNextSequence(SequenceDate, SequenceId)) 
) ON [PRIMARY] 
GO 

INSERT INTO SomeTable(SequenceDate) values ('2010-12-14') 
INSERT INTO SomeTable(SequenceDate) values ('2010-12-15') 
INSERT INTO SomeTable(SequenceDate) values ('2010-12-15') 
INSERT INTO SomeTable(SequenceDate) values ('2010-12-15') 
GO 

SELECT * FROM SomeTable 
GO 

SequenceId   SequenceDate SequenceNumber 
-------------------- ------------ ----------------- 
1     2010-12-14 20101214_00000001 
2     2010-12-15 20101215_00000001 
3     2010-12-15 20101215_00000002 
4     2010-12-15 20101215_00000003 

(4 row(s) affected) 

这是丑陋的，但工作的，对不对？ :-)没有任何临时表，没有意见，没有触发器，它会有一个体面的表现（当然，至少索引超过SequenceId和SequenceDate）。而你可以删除记录（因为和身份被用于结果计算字段）。

Answer 2

如果您不介意数字不是从1开始，您可以使用DATEDIFF(dd, 0, GETDATE())这是1-1-1900以来的天数。这将每天增加。

Answer 3

如果您创建的SequenceDate指数和SequenceId，我不认为将表现太糟糕了你可以做类似

CREATE TABLE SequenceTableStorage (
    SequenceId bigint identity not null, 
    SequenceDate date NOT NULL, 
    OtherCol int NOT NULL, 
) 

CREATE VIEW SequenceTable AS 
SELECT x.SequenceDate, (CAST(SequenceDate AS VARCHAR(10)) + '_' + RIGHT('0000000000' + CAST(SequenceID - (SELECT min(SequenceId) + 1 FROM SequenceTableStorage y WHERE y.SequenceDate = x.SequenceDate) AS VARCHAR(10)), 10)) AS SequenceNumber, OtherCol 
    FROM SequenceTableStorage x 

。

编辑：

如果事务插入一行上面的代码可能会错过一些序列号，例如，然后回滚（然后标识值将会丢失在空间）。

这个问题可以用这个视图来解决，这个视图的性能可能不够好，也可能不够好。

CREATE VIEW SequenceTable AS 
SELECT SequenceDate, (CAST(SequenceDate AS VARCHAR(10)) + '_' + RIGHT('0000000000' + row_number() OVER(PARTITION BY SequenceDate ORDER BY SequenceId) 
    FROM SequenceTableStorage 

我的猜测是，它会足够好，直到你开始获得每天数百万的序列号。

Answer 4

如果您可以创建具有不同名称的实际表格，并通过视图执行所有其他操作，那么它可能适合帐单。它也要求没有交易被彻底删除（所以你需要在视图/表中添加适当的触发/权限，以防止）：

create table dbo.TFake (
    T1ID int IDENTITY(1,1) not null, 
    T1Date datetime not null, 
    Val1 varchar(20) not null, 
    constraint PK_T1ID PRIMARY KEY (T1ID) 
) 
go 
create view dbo.T 
with schemabinding 
as 
    select 
     T1Date, 
     CONVERT(char(8),T1Date,112) + '_' + RIGHT('00000000' + CONVERT(varchar(8),ROW_NUMBER() OVER (PARTITION BY CONVERT(char(8),T1Date,112) ORDER BY T1ID)),8) as T_ID, 
     Val1 
    from 
     dbo.TFake 
go 
insert into T(T1Date,Val1) 
select '20101201','ABC' union all 
select '20101201','DEF' union all 
select '20101202','GHI' 
go 
select * from T 

结果：

T1Date T_ID Val1 
2010-12-01 00:00:00.000 20101201_00000001 ABC 
2010-12-01 00:00:00.000 20101201_00000002 DEF 
2010-12-02 00:00:00.000 20101202_00000001 GHI 

---

您当然也可以从视图中隐藏日期列，并将其默认为CURRENT_TIMESTAMP。

Answer 5

我试过这种方式来为用户日志和它的工作创建会话代码;

CREATE FUNCTION [dbo].[GetSessionSeqCode]() 
RETURNS VARCHAR(15) 
AS 
BEGIN 
DECLARE @Count INT; 
DECLARE @SeqNo VARCHAR(15) 

SELECT @Count = ISNULL(COUNT(SessionCode),0) 
FROM UserSessionLog 
WHERE SUBSTRING(SessionCode,0,9) = CONVERT(VARCHAR(8), GETDATE(), 112) 

SET @SeqNo = CONVERT(VARCHAR(8), GETDATE(), 112) +'-' + FORMAT(@Count+1,'D3'); 

RETURN @SeqNo 
END 

生成的代码是： '20170822-001' ， '20170822-002' ， '20170822-003'