Full type deduction for nulls in tuples

Detail name	Value
Changelog Number	9092
Type	Improvement
Status	Resolved
Fix Versions	Exasol 7.1.0
Resolution Date	2021-08-03

Problem

Starting with version 6.2.3, Exasol deduces the type of NULL in tuples based on constants. Its type deduction does not support expressions. This can lead to type errors.

Example:

SELECT * FROM VALUES ((1+1, TRUE), (NULL, FALSE)) AS t(i, b);

Workaround

It is possible to cast the null to the desired data type.
Example:

SELECT * FROM VALUES ((1+1, TRUE), (CAST(NULL AS INT), FALSE)) AS t(i, b);

Problem

Up to version 6.2.3, Exasol assumes that the type of NULL in tuples is BOOLEAN. This can cause type errors.

Example:

SELECT * FROM VALUES ((1, TRUE), (NULL, FALSE)) AS t(i, b);

Workaround

It is possible to cast the null to the desired data type.
Example:

SELECT * FROM VALUES ((1, TRUE), (CAST(NULL AS CHAR(1)), FALSE)) AS t(i, b);

With a full and fast type deduction such queries would not require casts.