15.00 - UDT-to-DATE Conversion - Teradata Database

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: FORMAT NAMED TITLE

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: FORMAT NAMED TITLE

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:

UPDATE

INSERT

Passing arguments to stored procedures, external stored procedures, UDFs, and UDMs

Specific system operators and functions identified in other sections of this book, unless the DisableUDTImplCastForSysFuncOp field of the DBS Control Record is set to TRUE

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 (non-CLOB)
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.