Could anyone tell why the sql can't execute smoothly? for e.g, select

Which database are you connecting to? I dont see any issue with your SQL statement but I've come across similar issue and I usually cast the output of my expression to the specified data type to make sure it is correct. However, please check if your database configuration is working correctly. If you are able to execute other SQL's without any issue and this is the only one giving issues, I'd quickly delete the node and replace it with another node with the same SQL and see if that resolves the problem. If not, please raise this with Appian Support.

Hi, sathya! Thank you!
I can execute this sql smoothly in database query client. I replaced the old node with a new one, but still can't work. It's so strange.

Another item to check would be if 'Database Connection' under Setup tab on the node is configured correctly.

Yeh,it's ok. if I don't use the concat function, it executed successfully.
Thanks!

What database are you using? Also, instead of specifying AS to your alias statement, can you try without it?

for e.g. concat(a,b) TEST, ...

Hi,sathya! Ours is mysql on cloud.
Still can't work with the same error message.
Thank you!