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Using databases
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Name | Description
Database Security | Databases often contain sensitive information. Different databases provide security schemes for protecting that information. Some databases, such as Paradox and dBASE, only provide security at the table or field level. When users try to access protected tables, they are required to provide a password. Once users have been authenticated, they can see only those fields (columns) for which they have permission. Most SQL servers require a password and user name to use the database server at all. Once the user has logged in to the database, that username and password determine which tables can be used. For information on providing... more
Referential Integrity, Stored Procedures, and Triggers | All relational databases have certain features in common that allow applications to store and manipulate data. In addition, databases often provide other, database-specific, features that can prove useful for ensuring consistent relationships between the tables in a database. These include Referential integrity. Referential integrity provides a mechanism to prevent master/detail relationships between tables from being broken. When the user attempts to delete a field in a master table which would result in orphaned detail records, referential integrity rules prevent the deletion or automatically delete the orphaned detail records. Stored procedures. Stored procedures are sets of SQL statements that are named... more
Transactions | A transaction is a group of actions that must all be carried out successfully on one or more tables in a database before they are committed (made permanent). If any of the actions in the group fails, then all actions are rolled back (undone). Transactions ensure that All updates in a single transaction are either committed or aborted and rolled back to their previous state. This is referred to as atomicity. A transaction is a correct transformation of the system state, preserving the state invariants. This is referred to as consistency. Concurrent transactions do not see each other's... more
Types of Databases | Relational database servers vary in the way they store information and in the way they allow multiple users to access that information simultaneously. Delphi provides support for two types of relational database server: Remote database servers reside on a separate machine. Sometimes, the data from a remote database server does not even reside on a single machine, but is distributed over several servers. Although remote database servers vary in the way they store information, they provide a common logical interface to clients. This common interface is Structured Query Language (SQL). Because you access them using SQL, they are sometimes called... more
Using Databases | Delphi includes many components for accessing databases and representing the information they contain. They are grouped according to the data access mechanism: The BDE page of the Component palette contains components that use the Borland Database Engine (BDE). The BDE defines a large API for interacting with databases. Of all the data access mechanisms, the BDE supports the broadest range of functions and comes with the most supporting utilities. It is the best way to work with data in Paradox or dBASE tables. However, it is also the most complicated mechanism to deploy. For more information about using the... more

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