Prepared Statements: CASE with parameter in WITH clause returns internal server error

Detail name	Value
Changelog Number	15025
Type	Bug
Status	Resolved
Affected Versions	Exasol 7.1.0, Exasol 8.0.0
Fix Versions	Exasol 8.0.6, Exasol 7.1.12
Resolution Date	2022-07-13

Description

In the following scenario, a query may return an internal server error:

• Query is used in a prepared statement
• The query contains a WITH clause
• A CASE expression is used within the WITH clause
• The THEN clause in the CASE expression contains a parameter

Example:

WITH
TEST AS
(
SELECT
CASE WHEN 1 IS NOT NULL
THEN ?
ELSE 'a'
END AS t1
)
SELECT *
FROM TEST;

Workaround

Cast the parameterized value to the proper data type. For example

WITH
TEST AS
(
SELECT
CASE WHEN 1 IS NOT NULL
THEN cast(? as VARCHAR(2000))
ELSE 'a'
END AS t1
)
SELECT *
FROM TEST;

Fix

The query succeeds as expected.