[Koha] Update a field using SQL

Hi am running Koha 3.18. I want to run some SQL queries to update some fields. When I try and run a simple query like UPDATE item SET PRICE = 2.00 WHERE BARCODE = '37000001' it just says executing query until I stop it. I am using MySQL Workbench from the Koha host and running under root user. Anything special I have to do? Thanks, Paul