Using Multiple Source Schemas
A single script often requires two schemas, one each for the source and target. It is also possible to use multiple schemas for the source data if all rows are UNION-compatible. Two schemas are UNION-compatible if their corresponding columns have exactly the same data type attributes (type, length, precision and scale); that is, other than their column names, the schemas are identical. If the schemas are UNION-compatible Teradata PT combines data from the sources, each being extracted by a different producer operator using a different schema, into a single output data stream using its UNION ALL feature. For information, see “UNION ALL: Combining Data from Multiple Sources” on page 221.
Example : Multiple Schemas in a Job Script
DEFINE SCHEMA ATTENDEES
DESCRIPTION 'Employees who attended the training session'
(
ATTENDEE_NAME CHAR(24),
TRAINING_FEEBACK VARCHAR(256)
);
DEFINE SCHEMA ABSENTEES
DESCRIPTION 'Employees who failed to attend the training session'
(
ABSENTEE_NAME CHAR(24),
EXCUSE VARCHAR(256)
);
DEFINE SCHEMA PRESENTERS
DESCRIPTION 'Employees who gave presentations at the training session'
(
PRESENTER_NAME CHAR(24),
PRESENTATION_TOPIC VARCHAR(128)
);
Explanation of Multiple Schema Example
Consider the following when referring to the proceeding multiple schema example: