UDT-to-DATE Conversion
Purpose
Converts a UDT expression to a DATE data type.
CAST Syntax
where:
Syntax element … |
Specifies … |
UDT_expression |
an expression that results in a UDT data type. For details on expressions that can result in UDT data types, see “SQL UDF” on page 1318. |
date_data_attribute |
one of the following optional data attributes: |
ANSI Compliance
This is ANSI SQL:2011 compliant.
As an extension to ANSI, CAST permits the use of data attribute phrases such as FORMAT.
Teradata Conversion Syntax
where:
Syntax element … |
Specifies … |
UDT_expression |
an expression that results in a UDT data type. For details on expressions that can result in UDT data types, see “SQL UDF” on page 1318. |
data_attribute |
one of the following optional data attributes: |
ANSI Compliance
This is a Teradata extension to the ANSI SQL:2011 standard.
Usage Notes
Data type conversions involving UDTs require appropriate cast definitions for the UDTs. To define a cast for a UDT, use the CREATE CAST statement. For more information on CREATE CAST, see SQL Data Definition Language.
Implicit Type Conversion
Performing an implicit data type conversion requires that an appropriate cast definition (see “Usage Notes”) exists that specifies the AS ASSIGNMENT clause.
Teradata Database performs implicit UDT-to-DATE conversions for the following operations:
If no UDT-to-DATE implicit cast definition exists, Teradata Database looks for other cast definitions that can substitute for the UDT-to-DATE implicit cast definition:
IF the following combination of implicit cast definitions exists … |
THEN Teradata Database … |
|
UDT-to-Numeric |
UDT-to-Character |
|
X |
|
uses the UDT-to-numeric implicit cast definition. If multiple UDT-to-numeric implicit cast definitions exist, then Teradata Database returns an SQL error. |
|
X |
uses the UDT-to-character implicit cast definition. If multiple UDT-to-character implicit cast definitions exist, then Teradata Database returns an SQL error. |
X |
X |
reports an error. |
Substitutions are valid because Teradata Database can use the implicit cast definition to cast the UDT to the substitute data type, and then implicitly cast the substitute data type to a DATE type.
Example
Consider the following table definition, where datetime_record is a UDT:
CREATE TABLE support
(id INTEGER
,information datetime_record );
Assuming an appropriate cast definition exists for the datetime_record UDT, the following statement converts the values in the information column to DATE:
SELECT id, CAST (information AS DATE) FROM support;
Related Topics
For details on data types and data attributes, see SQL Data Types and Literals.