Problem with concatenation

Why would version 4.2.2.1 of Libreoffice BASE keep giving me the following error when executing the query statement shown below:
Error - Invalid use of vertical bars

Statement - SELECT “TRIP_MILES” || ', ’ || “VEHICLE_ID” AS “Test” FROM “TripInfo”

Are you using the default HSQL database in embedded configuration?

Yes, I am using the HSQL database in embedded config. Why?

Nearly all reports of this error relate to use of an MS Access database, which is why I asked. Which version of HyperSQL are you using? The default one that comes with Base (v1.8.x) or the newer one (v2.x)? It is also worth noting that I cannot find that error message anywhere in the LO Base or HyperSQL source code, so it is probably a JDBC/SDBC message. Do you know which you are using? JDBC is preferred.

According to the FAQ here the comma between the two single quotation marks is not required. Have you tried it without this?

I have tried without the comma in quotes - same result.

Yes, according to this Apache OO forum post the comma should not present any problem anyway, I merely noticed this difference and thought I should mention it.

Although your SQL statement syntax looks OK, what happens if one value is NULL? Have you tried the SQL function CONCAT instead of using ‘||’? You might have to also use an inner COALESCE function to handle NULLS? See HERE.