I have 3 infotables, How to join infotables one after another as new infotable.

There are two OOTB code snippets or infotable functions that you could use.
You can find them in the Code Snippets InfoTableFunctions.

Method 1: If your infotables are based on the same datashape (or have the same fields) :

You can use the Union function to join two infotables with the same fields.

Method 2: If your infotables have different fields and you want to join them like in SQL.

You can use the Intersect function.

The same functions can also be found in the Javadoc, if you want to create your service in Java rather than in the composer.
Either way, you have to do 2 unions or 2 intersects. First to "combine" the first two infotables. The second command to join your 3rd infotable with the result of the first command.