SQL concepts

DB2^® UDB for iSeries™ SQL consists of these main parts.

• SQL runtime support

  SQL run-time parses SQL statements and runs any SQL statements. This support is that part of i5/OS™ licensed program, which allows applications that contain SQL statements to be run on systems where the DB2 UDB Query Manager and SQL Development Kit licensed program is not installed.

• SQL precompilers
  SQL precompilers support precompiling embedded SQL statements in host languages. The following languages are supported:

  • ILE C
  • ILE C++ for iSeries
  • ILE COBOL
  • COBOL for iSeries
  • iSeries PL/I
  • RPG III (part of RPG for iSeries)
  • ILE RPG
  The SQL host language precompilers prepare an application program containing SQL statements. The host language compilers then compile the precompiled host source programs. For more information about precompiling, see the topic Prepare and run a program with SQL statements in the Embedded SQL Programming information. The precompiler support is part of the DB2 UDB Query Manager and SQL Development Kit licensed program.
• SQL interactive interface

  SQL interactive interface allows you to create and run SQL statements. For more information about interactive SQL, see Use interactive SQL. Interactive SQL is part of the DB2 UDB Query Manager and SQL Development Kit licensed program.

• Run SQL Scripts

  The Run SQL Scripts window in iSeries Navigator allows you to create, edit, run, and troubleshoot scripts of SQL statements. Run SQL Scripts is a part of iSeries Navigator.

• Run SQL Statements CL command

  RUNSQLSTM allows you to run a series of SQL statements, which are stored in a source file. See Use the SQL statement processor for more information about the Run SQL Statements command.

• DB2 Query Manager for iSeries

  DB2 Query Manager for iSeries provides a prompt-driven interactive interface that allows you to create data, add data, maintain data, and run reports on the databases. Query Manager is part of the DB2 UDB Query Manager and SQL Development Kit licensed program. For more information, refer to the Query Manager Use book.

• SQL REXX Interface

  The SQL REXX interface allows you to run SQL statements in a REXX procedure. For more information about using SQL statements in REXX procedures, see the topic Code SQL statements in REXX applications in the Embedded SQL Programming information.

• SQL Call Level Interface

  DB2 UDB for iSeries supports the SQL Call Level Interface. This allows users of any of the ILE languages to access SQL functions directly through bound calls to a service program provided by the system. Using the SQL Call Level Interface, one can perform all the SQL functions without the need for a precompile. This is a standard set of procedure calls to prepare SQL statements, run SQL statements, fetch rows of data, and even do advanced functions such as accessing the catalogs and binding program variables to output columns.

  For a complete description of all the available functions and their syntax, see the SQL call level interface (ODBC) topic collection in the Database section of the iSeries Information Center.

• QSQPRCED API

  This application program interface (API) provides an extended dynamic SQL capability. SQL statements can be prepared into an SQL package and then run using this API. Statements prepared into a package by this API persist until the package or statement is explicitly dropped. For more information about the QSQPRCED API, see the QSQPRCED topic. For general information about APIs, see the i5/OS API topic.

• QSQCHKS API

  This API syntax checks SQL statements. For more information about the QSQCHKS API, see the QSQCHKS topic. For general information about APIs, see the i5/OS API topic.

• DB2 Multisystem

  This feature of the operating system allows your data to be distributed across multiple servers. For more information about DB2 Multisystem, see the DB2 Multisystem topic.

• DB2 UDB Symmetric Multiprocessing

  This feature of the operating system provides the query optimizer with additional methods for retrieving data that include parallel processing. Symmetric multiprocessing (SMP) is a form of parallelism achieved on a single system where multiple processors (CPU and I/O processors) that share memory and disk resource work simultaneously toward achieving a single end result. This parallel processing means that the database manager can have more than one (or all) of the system processors working on a single query simultaneously. See the topic Control parallel processing for queries in the Database Performance and Query Optimization topic for details on how to control parallel processing.

• SQL relational database and system terminology
  In the relational model of data, all data is perceived as existing in tables. DB2 UDB for iSeries objects are created and maintained as system objects.
• SQL and system naming conventions
  There are two naming conventions that can be used in DB2 UDB for iSeries programming: system (*SYS) and SQL (*SQL).
• Types of SQL statements
  There are several basic types of SQL statements. They are listed here according to their function.
• SQL communication area (SQLCA)
  An SQLCA is a set of variables that is updated at the end of the execution of every SQL statement.
• SQL diagnostics area
  The SQL diagnostics area is a set of information maintained by the database manager about the SQL statement that was most recently run. It can be accessed from your program by using the GET DIAGNOSTICS SQL statement.