I created a table called test
with column called code
:
create table test(
code char(3) not null);
I then populated the table with the following data:
insert into test values ('A12');
insert into test values ('B23');
insert into test values ('C45');
I then altered the column to make it char(4):
alter table test
alter column code char(4) not null;
I then added a 'X' to all existing data so that it becomes 4 characters long:
update test
set code='X'+code
where LEN(code)=3;
So far so good but then when I tried to add a check constraint:
alter table test
add constraint codeCheck check (code like 'A-Z''A-Z''0-9''0-9');
I got this error:
The ALTER TABLE statement conflicted with the CHECK constraint "codeCheck".
I understand that the error implies that the existing data violates the check constraint that I am trying to add into the table, but why?
and how do I do it such that the existing data and check constraint do not violate each other?
Your pattern syntax is wrong. It should be
alter table test
add constraint codeCheck check (code like '[A-Z][A-Z][0-9][0-9]');