How to restrict special characters < and > in input value for a column - plsql

Question

I am not that fluent in using regular expressions. I want that user should not provide value for a column with '<' or '>' in it.
Regards,
Sachin

Answer 1

Use group () and or | operators for example to validate user input you sould do:
set serveroutput on;
declare
l_value varchar2(32767) := '<p>test and data</p>';
begin
if regexp_like(l_value,'(<|>)','i') then
dbms_output.put_line('invalid');
else
dbms_output.put_line('valid');
end if;
end;
/
Good luck.

Answer 2

Use [ and ] to define a set of characters to match, e.g. [abc], [a-z], [a-z0-9_]
select string
, case
when regexp_like(string,'[<>]') then 'Invalid'
else 'Valid'
end as test
from
( select '<p>text</p>' as string from dual union all
select 'text' from dual );
STRING TEST
---------------- -------
<p>text</p> Invalid
text Valid
Or in PL/SQL:
declare
teststring varchar2(100) := '<p>test and data</p>';
regex varchar2(100) := '[<>]';
begin
dbms_output.put('"'||teststring||'"');
dbms_output.put(case when regexp_like(teststring,regex) then ' matches ' else ' does not match ' end );
dbms_output.put(regex);
dbms_output.new_line();
end;
/
"<p>test and data</p>" matches [<>]
PL/SQL procedure successfully completed
As a check constraint:
create table mytable
( col varchar2(20)
constraint mytable_ltgt_chk check ( not regexp_like(col,'[<>]') )
);
Test:
insert into mytable (col) values ('kitten > puppy');
rejected with:
ORA-02290: check constraint (MYRIAD_OWNER_82.MYTABLE_LTGT_CHK) violated
If you wanted to exclude square brackets as well, that would be:
constraint mytable_symbol_chk check ( not regexp_like(col,'[][<>]') );
Or without any regex:
constraint mytable_symbol_chk check ( col = translate(col,'[]<>','.') )
https://regex101.com/r/oQJztM/2/tests