Oracle 11g - Check constraint with RegEx

A check constraint follows the same syntax rules as conditions for a WHERE clause:

alter table foo
  add constraint check_email 
  check (REGEXP_LIKE(email,'your_regex_goes_here','I')); 

More details in the manual:

• for Oracle 11 - http://docs.oracle.com/cd/E11882_01/server.112/e41084/conditions007.htm#SQLRF52141
• for Oracle 12 - https://docs.oracle.com/database/121/SQLRF/conditions007.htm#SQLRF52141

Edit:

There are however some restrictions on what you can actually use in a check constraint:

• Oracle 11 - http://docs.oracle.com/cd/E11882_01/server.112/e41084/clauses002.htm#SQLRF52205
• Oracle 12 - https://docs.oracle.com/database/121/SQLRF/clauses002.htm#SQLRF52205

CREATE TABLE MYTABLE(
  EMAIL VARCHAR2(30) CHECK(REGEXP_LIKE (EMAIL,'^[A-Za-z]+[A-Za-z0-9.]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$'))
);

ALTER TABLE MYTABLE ADD(CONTACT NUMBER(10) CHECK(REGEXP_LIKE(CONTACT,'[0-9]{10}')));


Explanation of Regular Expression
^           #start of the line
  [_A-Za-z0-9-]+    #  must start with string in the bracket [ ], must contains one or more (+)
  (         #  start of group #1
    \\.[_A-Za-z0-9-]+   #     follow by a dot "." and string in the bracket [ ], must contains one or more (+)
  )*            #  end of group #1, this group is optional (*)
    @           #     must contains a "@" symbol
     [A-Za-z0-9]+       #        follow by string in the bracket [ ], must contains one or more (+)
      (         #      start of group #2 - first level TLD checking
       \\.[A-Za-z0-9]+  #        follow by a dot "." and string in the bracket [ ], must contains one or more (+)
      )*        #      end of group #2, this group is optional (*)
      (         #      start of group #3 - second level TLD checking
       \\.[A-Za-z]{2,}  #        follow by a dot "." and string in the bracket [ ], with minimum length of 2
      )         #      end of group #3
$           #end of the line