Lets say I have a table name that exists in my database and I store it on a loca

Not through expressions no. Although if you're returning meta data such as table names you might as well store the cdt name in your database somewhere. I can't think of a practical way to use this though... you're the king of ill-fitting requirements! ;-) Your requirements sound like you're keeping much of the system logic in the database such as validations etc. I've done this before with Appian and ended up with a web service layer with all the intelligence and a very empty Appian solution - not a great fit.

If you are using data store then you can create a data store entity constant and then you can use that constant

Hi Erick, you can use an @Table annotation in the .xsd file that defines the already created CDT. That tells Appian that the CDT should map to the table. Add the CDT as a data store entity in a data store and click "verify". You will learn whether the CDT "maps", or corresponds exactly, to the table. Go here for a listing of JPA Annotations that we can use in our .xsd files that define CDTs: forum.appian.com/.../Defining_a_Custom_Data_Type.html

Jack, thanks for the answer. How would I be able to use the @Table annotation within SAIL or process flow to figure out what the CDT is for a given String (table name)?

@erick, We can't have the annotation inside the SAIL component, we can defined multiple CDT's per each table and depending upon the input we can try to assign respective CDT type.. if you need to dynamically assign the local variable the use the type() constructor to assign to multiple CDT types.

So there is no way that given a String (table name), I can know what CDT is mapped to? And that table name is already created in the database.

as per my knowledge no.. the typeof(), typename() would give for Appian system data types but not CDT's.

What I am trying to do is to dynamically get the entity parameter for the function a!queryEntity(). Is there any way of doing that?

yes you can do this if you have predefined CDT, Data Stores defined, you can pass the entity as well as a parameter, defined constants of type Data Store Entity, one for each and using if else condition pass it.

@erickp I don't think that's possible OOTB. It might be worth trying to maintain the fact that a database table is associated with a particular datastore entity constant, in the database itself. This relationship will help you in obtaining a data store entity for a given table name. Off-course, you can also maintain this relationship in the expression rules.