Solution Guide for Migrating Oracle on UNIX to SQL Server - Willy .Net

<strong>Solution</strong> <strong>Guide</strong> <strong>for</strong> <strong>Migrating</strong> <strong>Oracle</strong> on UNIX to SQL Server on Windows 131Table 6.26 shows the implementation of the IDENTITY property feature in SQL Serverand what would be the equivalent in <strong>Oracle</strong>.Table 6.26: Implementation of <strong>Oracle</strong> Sequence in SQL Server<strong>Oracle</strong>CREATE SEQUENCE sequence_nameSTART WITH 1 INCREMENT BY 1CREATE TABLE table_name (column1NUMBER DEFAULTsequence_name.NEXTVAl,column2 …);INSERT INTO table_name (column2, …)VALUES ( … )CREATE TABLE table_name (column1NUMBER,column2 …);INSERT INTO table_name (column1,column2, …) VALUES(sequence_name.NEXTVAL, … )SQL Server-CREATE TA BLE table_name (column1NUMBER IDENTITY(1,1),column2 …);INSERT INTO table_name (column2, …)VALUES ( … )CREATE TABLE table_name (column1NUMBER IDENTITY(1,1),column2 …);INSERT INTO table_name (column2, …)VALUES ( … )One of the advantages of sequences being independent objects is that they can be usedto supply a unique identifier across multiple tables. This property of <strong>Oracle</strong> sequences isnot inherent in SQL Server’s IDENTITY property. If an identifier is required to be uniqueacross tables (or even databases across the globe), use the uniqueidentifier data type,which can be populated using the NEWID() function. The IDENTITY column can onlyhandle unique values and hence it cannot support the cycle feature of <strong>Oracle</strong> sequence.A maximum value also cannot be set but can be en<strong>for</strong>ced by choosing an appropriatesized data type <strong>for</strong> the IDENTITY column.Note There is no sufficient in<strong>for</strong>mation inside the <strong>Oracle</strong> database to figure out howand where a sequence is used. Hence the application's documentation, code, ordeveloper will have to be consulted to learn which sequence is used to populate acolumn. This in<strong>for</strong>mation is then used to define an IDENTITY column in that table.Database Links<strong>Oracle</strong> database links are used to <strong>for</strong>m a bridge between databases (instances). Remoteand distributed transactions can be executed against the remote database using thedatabase link. SQL Serverprovides similar functionality under the linked server.