UltraLite ActiveX User's Guide
Understanding UltraLite ActiveX Development
UltraLite databases (.udb files) are relational databases. They contain the following objects:
Tables A single UltraLite database can hold many tables. Relational database tables have a fixed number of columns, but can have any number of rows (up to a limit determined by the operating system). Each row has a single entry for each column. A NULL entry is used when there is no value for the entry. When designing your database, each table should represent a separate type of item, such as customers or employees.
For more information, see ULTable class.
Indexes The rows in a relational database table are not ordered. You can create indexes to access the rows in order. Indexes are commonly associated with a single column, but may also be associated with multiple columns.
For more information, see ULIndexSchema class.
Keys Each table has a special index called the primary key. Entries in the primary key column or columns must be unique.
Foreign keys relate the data in one table to that in another. Each entry in the foreign key column must correspond to an entry in the primary key of another table.
Primary keys and foreign keys ensure that the database has referential integrity. Referential integrity is enforced in UltraLite databases. For example, you cannot enter an order for a customer unless that customer exists in the database.
Publications A publications defines a set of data to be synchronized.
You must have a valid SQL Anywhere Studio license to synchronize the data in your UltraLite database with other databases. SQL Anywhere Studio includes MobiLink synchronization technology to synchronize UltraLite databases with desktop, workgroup, or enterprise databases.
For more information, see ULPublicationSchema class.
The database schema is a description of the database. It is the collection of tables, indexes, keys, and publications within the database, and all the relationships between them.
You do not alter the schema of an UltraLite database directly. Instead, you create a schema (.usm) file and upgrade the database schema from that file by calling a built-in UltraLite function in your application.
A schema file is also used in the initial creation of a database to specify the structure of the database.
Creating UltraLite database schema files
Upgrading your database schema