We have a major flaw in our mssql sql_concat_join function.

This works as expected:
SELECT 'X' + '-' + 'Y';
== Expected result: XY
== Actual result: XY

However, this does not:
SELECT 1 + '-' + 2;
== Expected result: 1-2
== Actual result: 3

We should be using the CONCAT() function:
SELECT CONCAT(1, '-', 2);
== Expected result: 1-2
== Actual result: 1-2

Unless we cast the integer to a string in this issue somehow (and we don't have a DML function to cast from int to string), then the fix for this is to actually CONCAT things in the CONCAT function. A pretty big change.

Thankfully the only uses of this are in the unit tests.