SQL Server 2017

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create table test (s varchar(30),
check (s not like '%[^a-zA-Z]%'))
insert into test values
('abc')
1 rows affected

insert into test values
(123)
Msg 547 Level 16 State 0 Line 1
The INSERT statement conflicted with the CHECK constraint "CK__test__s__35BCFE0A". The conflict occurred in database "fiddle_66012a6ab2934d4aadd2eb5a61053dc1", table "dbo.test", column 's'.
Msg 3621 Level 0 State 0 Line 1
The statement has been terminated.

insert into test values
('ac!')
Msg 547 Level 16 State 0 Line 1
The INSERT statement conflicted with the CHECK constraint "CK__test__s__35BCFE0A". The conflict occurred in database "fiddle_66012a6ab2934d4aadd2eb5a61053dc1", table "dbo.test", column 's'.
Msg 3621 Level 0 State 0 Line 1
The statement has been terminated.

insert into test values
('a1c')
Msg 547 Level 16 State 0 Line 1
The INSERT statement conflicted with the CHECK constraint "CK__test__s__35BCFE0A". The conflict occurred in database "fiddle_66012a6ab2934d4aadd2eb5a61053dc1", table "dbo.test", column 's'.
Msg 3621 Level 0 State 0 Line 1
The statement has been terminated.

select * from test


s


abc