Categories of SQL Statements

SQL statements are traditionally divided into the following logical categories:

• Data definition statements. These data definition language (DDL) statements can declare, rename, modify, or destroy objects in the local database.
• Data manipulation statements. These data manipulation language (DML) statements can retrieve, insert, delete, or modify data values.
• Cursor manipulation statements. These statements can declare, open, and close cursors, which are data structures for operations on multiple rows of data.
• Dynamic management statements. These statements support memory management and allow users to specify at runtime the details of DML operations.
• Data access statements. These statements specify access privileges and support concurrent access to the database by multiple users.
• Data integrity statements. These implement transaction logging and support the referential integrity of the database.
• Optimization statements. These can be used to improve the performance of operations on the database.
• Routine definition statements. These can declare, define, modify, execute, or destroy user-defined routines that the database stores.
• Client/server connection statements. These can open or close a connection between a database and a client application.
• Auxiliary statements. These can provide information about the database. (This is also a residual category for statements that are not closely related to the other statement categories.)
• Optical subsystem statements. These statements are separately documented in IBM Informix Optical Subsystem Guide.

The SQL statements of each category are listed in the pages that follow.

As Chapter 2 indicates, some statements (and some statement options, as noted in the syntax diagrams) are specific to Dynamic Server (sometimes abbreviated as "IDS") or are specific to Extended Parallel Server (sometimes abbreviated as "XPS").