轉：SqlServer2012自增列值忽然增大1000的緣由及解決方法

原文連接：http://blog.csdn.net/phoenix36999/article/details/53304126 

首先排除數據回滾及增長刪除等操做。 

按照這篇文章SQL Server 2012 Auto Identity Column Value Jump Issue的方法，就能夠解決問題了。 

如下是內容：

Introduction

From SQL Server 2012 version, when SQL Server instance is restarted, then table's Identity value is jumped and the actual jumped value depends on identity column data type. If it is integer (int) data type, then jump value is 1000 and if big integer (bigint), then jump value is 10000. From our application point of view, this increment is not acceptable for all the business cases specially when the value shows to the client. This is the special case/issue ships with only SQL Server 2012 and older versions have no such issue.

從SQL Server2012版本中，當SQL Server實例從新啓動，則表的IDENTITY值跳起來，實際跳下值取決於標識列的數據類型。若是它是整數（INT）數據類型，而後跳到值是1000，若是大的整數（BIGINT），而後跳值爲10000。從咱們的應用程序的角度來看，這個增量在全部的商業案例中是沒法接受的，特別是當值展現給客戶端時。這是特殊狀況，問題僅隨SQL Server 2012，舊版本有沒有這樣的問題。

Background

A few days ago, our QA Engineer claims that one of our table's identity column jumped 10000. That means the last identity value of that table was 2200 now it is 12001. In our business logic is like that the value shows to the client and it will not be accepted by the client. So we must solve the issue.

Using the Code

The first time, we all are surprised and confused as to how it is possible? We usually do not insert any value in identity column (insert value to identity column is possible). The identity value is maintained by SQL Server itself. One of our core team members started investigation the issue and found out the solution. Now, I want to elaborate the issue and solution that was found out by my colleague.

How to Reproduce That?

You need to setup SQL Server 2012 and create a test database. Then create a table with auto identity column:

create table MyTestTable(Id int Identity(1,1), Name varchar(255));

Now insert 2 rows there:

insert into MyTestTable(Name) values ('Mr.Tom');
insert into MyTestTable(Name) values ('Mr.Jackson');

You see the result:

SELECT Id, Name FROM MyTestTable;

The result is as expected. Now just restart your SQL Server service. There are various ways in which you can do it. We did it from SQL Server management studio.

Now, insert another 2 rows to the same table again:

insert into MyTestTable(Name) values ('Mr.Tom2');
insert into MyTestTable(Name) values ('Mr.Jackson2');

Now see the result:

SELECT Id, Name FROM MyTestTable;

Now you see that after restarting the SQL Server 2012 instance, then identity value starts with 1002. It means it jumped 1000. Previously, I said that we also see if the data type of that identity column is bigint, then it will jump 10000.

Is it really a bug?

Microsoft declares it is a feature rather than a bug and in many scenarios it would be helpful. But in our case, it would not be acceptable because that number is shown to the client and the client will be surprised to see that new number after jump and the new number depends on how many times SQL Server is restarted. If it is not visible to the client, then it might be acceptable so that the number is used internally.

Solutions  解決方法

If we are not interested in this so called feature, then we can do two things to stop that jump.

• Using Sequence  方法一：使用序列
• Register -t272 to SQL Server Startup Parameter  方法二：註冊-t272到SQL Server啓動參數

Using Sequence

First, we need to remove Identity column from tables. Then create a sequence without cache feature and insert number from that sequence. The following is the code sample:

CREATE SEQUENCE Id_Sequence
    AS INT
    START WITH 1
    INCREMENT BY 1
    MINVALUE 0
    NO MAXVALUE
   NO CACHE
insert into MyTestTable values(NEXT VALUE FOR Id_Sequence, 'Mr.Tom'); 
insert into MyTestTable values(NEXT VALUE FOR Id_Sequence, 'Mr.Jackson'); 

Register -t272 to SQL Server Startup Parameter

Open SQLServer configuration manager from your server. Select SQL Server 2012 instance there right client and select Properties menu. You will find a tabbed dialog window. You select start up parameters tab from there and register -t272. Then restart SQL Server 2012 instance again and see the difference:

打開SQLServer configuration manager。左邊選擇服務。右邊在對應實例右鍵選擇屬性。點擊啓動參數。把-t272添加進去。重啓sqlserver服務。再次新增數據進行觀察。

Points of Interest

If too many tables contain identity column to your database and all contain existing values, then it is better to go for solution 2. Because it is a very simple solution and its scope is server wise. This means if you add SQL Server 2012 parameter -t272 there, then it will affect all your databases there. If you want to create a new database and you need auto generated number field, then you can use solution 1, that means use sequence value to a column instead of auto Identity value. There are so many articles you can find online about when you will use auto identity column when using sequence and advantages/disadvantages of each other. I hope you will read all those and take the appropriate decision.

若是您的數據庫表包含太多的標識列，而且全部的表都包含現有的值，那麼最好是去用解決方案2。由於它是一個很是簡單的解決方案，它的範圍是服務器。這意味着若是你添加SQL Server 2012參數- t272，而後它會影響你全部的數據庫裏。

若是你想建立一個新的數據庫，你須要自動生成的數字字段，那麼你可使用解決方案1，這意味着使用序列值的列，而不是自動識別值。

有這麼多的文章，你能夠找到網上關於當你將使用自動識別列時，使用序列和優點/劣勢的對方。我但願你會閱讀全部這些，並採起適當的決定。