Example: LOB Support in a UNION ALL Query - Analytics Database - Teradata Vantage

SQL Data Manipulation Language

Deployment
VantageCloud
VantageCore
Edition
Enterprise
IntelliFlex
VMware
Product
Analytics Database
Teradata Vantage
Release Number
17.20
Published
June 2022
Language
English (United States)
Last Update
2024-04-05
dita:mapPath
pon1628111750298.ditamap
dita:ditavalPath
qkf1628213546010.ditaval
dita:id
esx1472246586715
lifecycle
latest
Product Category
Teradata Vantage™

Previously, columns with CLOB or BLOB data type were not allowed in any set operation query, as it is not possible to hash on a CLOB or BLOB column. UNION ALL does not need to hash on any column (including a LOB), that restriction is removed with the the UNION ALL optimizations feature.

Assume the following tables:

CREATE TABLE t_blob1 (a1 INTEGER, b1 BLOB(2097088000));
CREATE TABLE t_clob2 (a2 INTEGER, b2 CLOB);

Consider the following query:

-- Prior to Teradata Database 16.0:
SELECT b1 FROM t_clob1
UNION ALL
SELECT b2 FROM t_clob2;

Result:

*** Failure 5690 LOBs are not allowed to be hashed.
                Statement# 1, Info = 0
-- Teradata Database 16.0:
SELECT b1 FROM t_clob1 
UNION ALL 
SELECT b2 FROM t_clob2;

Result:

*** Query completed.  8 rows found.