Using TDataSet descendants classifies TDataSet descendants by the method they use to access their data. Another useful way to classify TDataSet descendants is to consider the type of server data they represent. Viewed this way, there are three basic classes of datasets:
Table type datasets: Table type datasets represent a single table from the database server, including all of its rows and columns. Table type datasets include TTable, TADOTable, TSQLTable, and TIBTable.
Table type datasets let you take advantage of indexes defined on the server. Because there is a one-to-one correspondence between database table and dataset, you can use server indexes that are defined for the database table. Indexes allow your application to sort the records in the table, speed searches and lookups, and can form the basis of a master/detail relationship. Some table type datasets also take advantage of the one-to-one relationship between dataset and database table to let you perform table-level operations such as creating and deleting database tables.
Query-type datasets: Query-type datasets represent a single SQL command, or query. Queries can represent the result set from executing a command (typically a SELECT statement), or they can execute a command that does not return any records (for example, an UPDATE statement). Query-type datasets include TQuery, TADOQuery, TSQLQuery, and TIBQuery.
To use a query-type dataset effectively, you must be familiar with SQL and your server's SQL implementation, including limitations and extensions to the SQL-92 standard. If you are new to SQL, you may want to purchase a third party book that covers SQL in-depth. One of the best is Understanding the New SQL: A Complete Guide, by Jim Melton and Alan R. Simpson, Morgan Kaufmann Publishers.
Stored procedure-type datasets: Stored procedure-type datasets represent a stored procedure on the database server. Stored procedure-type datasets include TStoredProc, TADOStoredProc, TSQLStoredProc, and TIBStoredProc.
A stored procedure is a self-contained program written in the procedure and trigger language specific to the database system used. They typically handle frequently repeated database-related tasks, and are especially useful for operations that act on large numbers of records or that use aggregate or mathematical functions. Using stored procedures typically improves the performance of a database application by:
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