sql server auto increment primary key

Misunderstanding of SQL Server clustered index and primary key Many people may mix the primary key and clustered index, or think this is the same thing. This concept is very incorrect. A

GO--determine if the table exists in the way 1if object_id(N'Ef_user'N'U') is NULL--determine if the table exists in the way 2--If not EXISTS (SELECT * FROM dbo. SysObjects WHERE id = object_id (N ' [Ef_user] ') and OBJECTPROPERTY (ID, ' istable ') = 1)begin--directly create a table with the self-increment and specify a PRIMARY KEY constraintCREATE TABLE [dbo].[E

Original: Deletes all indexes of the specified table, including primary key indexes, unique indexes, and normal indexes, for SQL Server 2005.Deletes all indexes of the specified table, including primary key indexes, unique indexes

Many people may confuse PrimaryKey with clustered index, or think this is the same thing. This concept is very incorrect. A primary key is a constraint attached to an index. This index can be a clustered index or a non-clustered index. So on one (or a group) Field Many people may confuse Primary Key with clustered ind

B, LAST_INSERT_ID will change.Max (id) is obviously unavailable when multiple users insert data alternately.This should use LAST_INSERT_ID, because LAST_INSERT_ID is based on Connection, as long as each thread uses an independent Connection object, the LAST_INSERT_ID function returns the ID of the first record generated by the Connection for the latest insert or update * of the AUTO_INCREMENT column. This value cannot be affected by connections of other clients. This ensures that you can retrie

auto_increment after insert:The InsertRow () method provided by JDBC2.0The Getgeneratedkeys () method provided by JDBC3.0Through the SQL Select LAST_INSERT_ID () functionThrough the SQL @ @IDENTITY variable1. The InsertRow () method provided by JDBC2.0Since jdbc2.0, this can be done in the following way. The code is as follows Copy Code Statement stmt = null;ResultSet rs = n

the primary key is not specified as a clustered index, the table may still be managed in a heap, inefficient about sorting and repeating values :sort : When you create a composite index, you specify multiple fields, which is the order in which the index order is sorted?is sorted by the first field on the indexThe sort order for this index is sorted by the ID field.1 CREATE INDEX TEMPPKNCL_ID_NCL on [

Label:How to obtain primary foreign key relationships in SQL Server 2008:Transferred from: http://www.cnblogs.com/ke10/archive/2012/06/11/2544655.htmlSELECT object_name (con.constid) ' Relationship name ',object_name (Sf.fkeyid) ' primary

Tomcat engines to get the primary key at the same time is equivalent to extracting the same value in concurrency without synchronized protection, and then inserting will cause the dumplicate entry error.Later I checked the hibernate reference and mentioned that the increment should not be used in the cluster.After the problem is found, the solution is very simpl

A problem found during development last week ~~ When nhib.pdf is used, the problem of multiple constraints in a table is stuck for one day, which may be due to poor foundation ~ I am not familiar with the use of the joint primary key and nhib.pdf. It took a day and wasted a day. It is very complicated to use the Union primary

Label:Add the settings for the database multi-field composite primary key.First, a table cannot have more than one primary key. But there are multiple fields that can be combined into one primary key, which is why sometimes the table has multiple fields with a

SQL Server database primary key self-increment insert display valueA few days ago at work encountered in the deletion of the database table data, when deleted, the re-added data did not get the original data ID value (the table ID is the

transactions. The user name is written to the users table, and the department it owns is written to the Userdepart table, and the transaction mechanism is used to ensure that the two steps either succeed at the same time or fail at the same time. The problem is that when the first step is complete, we don't know what the value of the Id_user to write to the second step, because this value is automatically generated by SQL

SQL primary key constraints and foreign key constraints, SQL primary key constraintsPrimary key constraint

generated by Ethernet card address, nanosecond time, chip ID code, and many possible digits. The format is: 04755396-9a29-4b8c-a38d-00042c1b9028. The advantage of a GUID is that the generated ID is unique, whether you are exporting data or doing step-by-step development, there is no problem. However, it generates a long ID, the database space to occupy more, with the loss of external storage prices, this also need not be considered. In addition, the GUID is not easy to remember, in this regard