Primary Key Generation Using Oracle's Sequence
- Primary Key Generation Using Oracle's Sequence. 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 @AutomaticKeyGeneration annotation to point to this table.
- Apr 20, 2006 In SQL terms, a candidate key is any combination of columns that uniquely identifies a row (SQL and the relational model aren’t the same thing, but I’ll put that aside for this article). The data’s primary key is the minimal candidate key. Many people think a primary key is something the DBA defines, but that’s not true.
- Feb 12, 2017 UUID or GUID as Primary Keys? (bound) to our SQL Server databases, which is fine — we’re in the same company. Still, in order to disambiguate colliding sequence keys from our multiple databases, we generate a pseudo-primary-key by concatenating two values, the id (PK).
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 @AutomaticKeyGeneration annotation to point to this table.Generate new ssh public key mac terminal. It is highly recommended to use the -o option as the new OpenSSH format has an increased resistance to brute-force password cracking. The -o option instructs ssh-keygen to store the private key in the new OpenSSH format instead of the old (and more compatible PEM format).
SQL SERVER 2012 – Changing a table from identity to sequence (Automatically) February 16, 2013 by Muhammad Imran In my last article, I had discussed how to convert a table from identity to sequence (manually).
In your Oracle database, you must create a sequence table that will create the primary keys, as shown in the following example:
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This creates a sequences of primary key values, 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 cacheSize attribute of the @AutomaticKeyGeneration annotation:
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 @JarSettings Annotation. For more information on the definition of a CMP entity bean, see below.
Primary Key Generation Using SQL Server's IDENTITY
In SQL Server 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 @JarSettings Annotation. For more information on the definition of a CMP entity bean, see below.
Primary Key Generation Using a Named Sequence Table
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: Generate self signed certificate with private key west.
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: Generate ssh key github.
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 @JarSettings Annotation. For more information on the definition of a CMP entity bean, see the next section.
Note. When you specify a cacheSize value 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.
Defining the CMP Entity Bean
When defining a CMP entity bean that uses one of the primary key generators, you use the @AutomaticKeyGeneration annotation to point to the name of the primary key generator table to obtain primary keys. 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 described above, and that ejbCreateSet Primary Key Sql Server
method does not take a primary key:Sql Server Create Primary Key
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