Question

I want to insert a constant called TUC and concatenate it with the initials of FirstName and LastName id of table.

id – 1
fname – James
lname – Bond

id – 2
fname – Daniel
lname – Edgar

eg. TUCJB001, TUCDE002,….

Answer 1

something like this

update tab 
SET newid=CONCAT('TUC', LEFT(fname, 1), LEFT(lname, 1), LPAD(id,03, '0'));

Demo

Note If you want 4 digit number you will need do changes as highlighted below.

update tab 
SET newid=CONCAT('TUC', LEFT(fname, 1), LEFT(lname, 1), LPAD(id,digit_range, '0'));
                                                                ^^^^^^^^^^^