There is no command in CL to allow you to update a DB,
There are a number of free RUNSQL commands that you can download fromj from the web. They allow you to build your SQL statment on the fly in CL and then run it.
Here is a link to one of them, there are others.
There are most certainly CL commands to update a database. The rather lengthy list of database related commands can be found at CL for Files. There are commands to Update (UPDRCDCLF)/Delete(DLTRCDCLF)/Write(WRTRCDCLF) database records (in addition to subfile support, printer support, etc). In fact you can do things in CL with database that is not available with RPG, COBOL, or C! You do need to be at V5R4 or later.
If you are not interested in spending any money, just use the free run-time support that can be downloaded from the referenced site. The commands supported can be found at the page referenced earlier under Using only Run-Time Commands.
If you want to get the most productivity out of your development time, there is a fee-based precompiler that is packaged as a separate option of CL for Files. The precompiler provides, among other things, DCLF like commands to access the external descriptions of your files, commands named like RPG opcodes (CHAIN/UPDATE/etc — which it would appear doesn’t apply in your case), etc. The one time charge for the precompiler is $795 regardless of the size of your system.
As the developer of the product I do receive compensation for sales of the precompiler.
—End vendor response