Oracle provides the 'sequence' utility to automatically generate unique primary keys. To use this utility to auto-generate primary keys for a CMP entity bean, you must create a sequence table and use the ejbgen:automatic-key-generation tag to point to this table.
The first is PRIMARY KEY, which as the name suggests, forces the specified column to behave as a completely unique index for the table, allowing for rapid searching and queries. While SQL Server only allows one PRIMARY KEY constraint assigned to a single table, that PRIMARY KEY can. Your database primary key should NEVER have business meaning. It should be meaningless by definition. So add the GUID as your business key, and a normal primary key (usually a long int) as the database primary key. You can always put a unique index on the GUID to ensure uniqueness. AUTO INCREMENT Field. Auto-increment allows a unique number to be generated automatically when a new record is inserted into a table. Often this is the primary key field that we would like to be created automatically every time a new record is inserted. I have a table set up that currently has no primary key. All I need to do is add a primary key, no null, autoincrement. I'm working with a Microsoft SQL Server database. I understand that it can't be done in a single command but every command I try keeps returning syntax errors. Jan 07, 2020 And then add primary key constraint. ALTER TABLE autoincrementtb ADD ( CONSTRAINT autoincrementtbpk PRIMARY KEY (id) ); Now we will create a sequence to generate unique auto incremented values. A sequence is a data object that can be used by multiple users to generate auto increment values(no duplicate values will be generated). May 25, 2016 The best way to auto generate an ID for the primary key field will be by the us of a sequence database object. Sequences will never generate a gap free sequence of numbers purposefully. It happens in some scenario like. 1) I f we call seq.nextval and doesn't insert the value somewhere (or).
In your Oracle database, you must create a sequence table that will create the primary keys, like is shown in the following example:
This creates a sequences of primary key, starting with 1, followed by 2, 3, and so forth. The sequence table in the example uses the default increment 1, but you can change this by specifying the increment keyword, such as increment by 3. When you do the latter, you must specify the exact same value in the cache-size attribute of the ejbgen:automatic-key-generation tag:
If you have specified automatic table creation in the CMP bean's project settings, the sequence table will be created automatically when the entity bean is deployed. For more information, see @ejbgen:jar-settings Annotation. For more information on the definition of a CMP entity bean, see below.
In SQL Server (2000) you can use the 'IDENTITY' keyword to indicate that a primary-key needs to be auto-generated. The following example shows a common scenario where the first primary key value is 1, and the increment is 1:
In the CMP entity bean definition you need to specify SQLServer(2000) as the type of automatic key generator you are using. You can also provide a cache size:
If you have specified automatic table creation in the CMP bean's project settings, the sequence table will be created automatically when the entity bean is deployed. For more information, see @ejbgen:jar-settings Annotation. For more information on the definition of a CMP entity bean, see below.
Note. The SQLServer2000 option is the same as SQLServer, except that SQLServer uses @@IDENTITY column to get the generated key value and SQLServer2000 uses the SCOPE_IDENTITY() function instead.
A named sequence table is similar to the Oracle sequence functionality in that a dedicated table is used to generate primary keys. However, the named sequence table approach is vendor-neutral. To auto-generate primary keys this way, create a named sequence table using the two SQL statements shown in the example:
In the CMP entity bean definition you need to specify the named sequence table as the type of automatic key generator you are using. You can also provide a cache size:
If you have specified automatic table creation in the CMP bean's project settings, the sequence table will be created automatically when the entity bean is deployed. For more information, see @ejbgen:jar-settings Annotation. For more information on the definition of a CMP entity bean, see the next section.
Note. When you specify a cache-size for a named sequence table, a series of unique values are reserved for entity bean creation. When a new cache is necessary, a second series of unique values is reserved, under the assumption that the first series of unique values was entirely used. This guarantees that primary key values are always unique, although it leaves open the possibility that primary key values are not necessarily sequential. For instance, when the first series of values is 10..20, the second series of values is 21-30, even if not all values in the first series were actually used to create entity beans.
When defining a CMP entity bean that uses one of the primary key generators, you point to the name of the primary key generator table to obtain primary keys, using the ejbgen:automatic-key-generation tag. Also, you must define a primary key field of type Integer or Long, to set and get the auto-generated primary key. However, the ejbCreate method does not take a primary key value as an argument. Instead the EJB container adds the correct primary key to the entity bean record.
The following example shows what the entity bean might look like. Notice that the bean uses the named sequence option describe above, and that ejbCreate method does not take a primary key:Related Topics
Jul 12, 2013 12:52 AMRagavanBLINK
Hi Manish,
try like this sample,
Personal detail:
create table personaldetail(id bigint identity primary key,pid nvarchar(20) unique,name nvarchar(25),addres nvarchar(100)) Product key generator free download for windows 7 to 10.
Occupation:
create table occupation(id bigint identity primary key,pid nvarchar(20) references personaldetail(pid),occupation nvarchar(25),dept nvarchar(25))
then generate the pid at code behind like,
public string generate_ID(){
int id=0;
string pid;
string pidquery = 'select top 1 SUBSTRING(pid,4,len(piid))as pid from personal detail order by pid desc';
// here 4 char denotes number after prefix string('HUA')
SqlCommand scmd = new SqlCommand(pidquery, con);
SqlDataAdapter adapter = new SqlDataAdapter(pidquery, con);
DataTable restable = new DataTable();
adapter.Fill(restable);
if (restable.Rows.Count > 0)
{
SqlDataReader reader = scmd.ExecuteReader();
reader.Read();
id= Convert.ToInt32(reader['pid']);
id= id+ 1;
pid = 'HUA' + Convert.ToString(id);
}
else // its for if no data in db
{
id= 1;
pid = 'HUA' + Convert.ToString(jid);
}
return pid;
}
after got id:
insert into both tables like:
1. insert into personaldetail('+pid+','+name+','+addr+')
2.insert into occupation('+pid+','+occupation+','+dept+')
please let me know the status.
Thank you,