Thursday, September 24, 2009

(Query/400 Tutorial) Query/400 fundamentals

Several elements on your system organize and store information, or data, so that you and other system users can work with it to get the results that you need. The following topics introduce those elements, tell you about them and how they relate to you and Query, and direct you to other publications where you can find more information.

Files, fields, and record formats in Query/400
Information, or data, is organized and stored on your system in various forms, primarily in objects called database files (usually referred to as just files). A file contains individual units of information, called records, that each contain related pieces of data. Each piece of information in a record is called a field, and how the fields are organized is defined in a record format (often just called a format).

When you run a query to produce a report, Query uses the files, fields, and record formats to get the information you want from the database, in the form of records, and uses those records to produce a query report.

Double-byte character set (DBCS) fields in Query/400
Some countries use pictographs or symbolic characters in their language. DBCS fields must be used for such data. As a general rule, if your national language uses single-byte character set (SBCS) characters, your files do not contain DBCS data. You can ignore any on-line help information that refers to DBCS data.

1. To properly display DBCS data, you need a DBCS-capable display.
2. In Query, the following naming convention is used for DBCS data:
- Character data refers to both SBCS and DBCS character data.

- DBCS data refers to any type of DBCS data, including bracketed-DBCS and DBCS-graphic data types.
- Bracketed DBCS refers to DBCS-open, DBCS-either, or DBCS-only data types.

UCS2 level 1 character set support in Query/400
UCS2 Level 1 is a 16-bit encoding for graphic characters. When doing business in a worldwide environment you need the ability to enter and process data from more than one national language. For example, a list of customer names may contain German, Greek, English, and Thai characters that must be printed or displayed on the same device at the same time.

Query/400 treats UCS2-graphic data the same as GRAPHIC or VARGRAPHIC data. A UCS2-graphic field is a DBCS-graphic field tagged with a UCS2 CCSID.

The VARCHAR and VARGRAPHIC functions help you write queries that include UCS2 data.

Data definition languages and utilities support in Query/400
Query can query data in files that are created using different data definition languages or products. Although the description given above applies to all the files on your system, the names or concepts that might be used depend on the programming language or product (like IDDU, DDS, and DB2 UDB for iSeries) that is used to define the files.

You Might Also Want To Visit The Following Tutorial Posts:
AS/400 For Dummies
AS/400 Tutorial
SQL/400 Tutorial
Query/400 Tutorial

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