Question

I have a field X in my database which contains text values. My values are all ascii (between 0-255 ascii code), I would like to decrement all my values.
If we have for instance ‘1’ as the text, it should be ‘0’ instead. At first I wanted to use the function ASCII and CHAR but they are not available in sqlite. Any tips ?

Answer 1

If your values are all a single character, you can use a table of replacement values; here’s a partial example:

sqlite> create table m1 (c,p);
sqlite> insert into m1 values ('b','a');
sqlite> insert into m1 values ('c','b');
sqlite> insert into m1 values ('d','c');
sqlite> create table tst (x);
sqlite> insert into tst values ('c');
sqlite> insert into tst values ('c');
sqlite> insert into tst values ('d');
sqlite> insert into tst values ('d');
sqlite> select * from tst;
c
c
d
d
sqlite> update tst set x = (select p from m1 where c = x);
sqlite> select * from tst;
b
b
c
c
sqlite> 

You’d have to flesh out the m1 table for all possible values.