Data truncated for column?

After changing the data type of a MySql column in order to store Twilio call ids (34 char strings), I try to manually change the data in that column with:

update calls 
   set incoming_Cid='CA9321a83241035b4c3d3e7a4f7aa6970d' 
 where id='1';

However I get an error which doesn't make sense seeing as the column's data type was properly modified?

| Level ||| Code | Message | Warning | 1265 | Data truncated for column 'incoming_Cid' at row 1

Your problem is that at the moment your incoming_Cid column defined as CHAR(1) when it should be CHAR(34).

To fix this just issue this command to change your columns' length from 1 to 34

ALTER TABLE calls CHANGE incoming_Cid incoming_Cid CHAR(34);

Here is SQLFiddle demo

I had the same problem because of an table column which was defined as ENUM('x','y','z') and later on I was trying to save the value 'a' into this column, thus I got the mentioned error.

Solved by altering the table column definition and added value 'a' into the enum set.