How to access Db2 via Node-RED flow

I would like to know How to access Db2 via Node-RED flow.

In IBM Cloud, I launched an application using catalogue named " Node-RED". That application is deployed with Cloudant by default. Creating Node-RED flow, I tried to get / insert data from Cloudant, and it worked well.

After that, I created a Db2 service and connected it to that application. I created a table in that Db2 service for testing and insert some records in it. I edit Node-RED flow to try to get the data from Db2 table for testing, but it did not work well. Neither connecting by Service name, nor connecting by selecting "External Db2" and set connection information.

Does Node-RED in IBM Cloud not work well with Db2?

Does anyone provide some advice to solve this problem?