A schema is a set of metadata definitions about the columns and rows of a data source or destination object. As such, a schema may include definitions for the following types of sources and objects:
- Data types and column sizes
- Precision, scale, and null-value indicators
- Database tables, columns and rows
Teradata PT uses schema definitions, which are similar to SQL table definitions. The following schema definitions are used in Teradata PT:
- Represent virtual tables. They do not have to correspond to any actual tables in the database.
- Contain column definitions: names and data types.
- Act as reusable templates
- Describe the contents of various data sources and targets, such as files, relational tables, etc.
- Are similar to record layout definitions used by the Teradata standalone load and unload utilities.
The following is an example of a schema definition:
DEFINE SCHEMA FREQ_FLYER_SRC DESCRIPTION ‘SCHEMA FOR FREQUENT FLYER SOURCE FILE’ ( RES_ID VARCHAR(14), FLIGHT_NO SMALLINT, ORIGIN CHAR(3), DEST CHAR(3), TKT_ID CHAR(12) TKT_ISSUE_DATE ANSIDATE, TKT_AMT DECIMAL(5,2), TRAVEL_AGCY_ID CHAR(4), FREQ_MILES_ID CHAR(8) );