LIKE, NOT LIKE

LIKE operator searches a string for a pattern. The patterns can have the following two wildcard characters:

Item	Description
Underscore (_)	Matches one character in a specified position
Percent (%)	Matches any number of characters

For example, '_A%' matches any one character in the first position, the A matches an A character in the second position, and the percent (%) matches any characters following the A character.

CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
                      ENAME VARCHAR2(10),
                      HIREDATE DATE);

INSERT INTO EMP VALUES (1, 'SMITH', TO_DATE('17-DEC-1980', 'DD-MON-YYYY'));
INSERT INTO EMP VALUES (2, 'ALLEN', TO_DATE('20-FEB-1981', 'DD-MON-YYYY'));
INSERT INTO EMP VALUES (3, 'WARD',  TO_DATE('22-FEB-1981', 'DD-MON-YYYY'));
INSERT INTO EMP VALUES (4, 'JONES', TO_DATE('2-APR-1981',  'DD-MON-YYYY'));
INSERT INTO EMP VALUES (5, 'MARTIN',TO_DATE('28-SEP-1981', 'DD-MON-YYYY'));

SQL> select * from emp where ename like '_A%';

     EMPNO ENAME      HIREDATE
---------- ---------- ---------
         3 WARD       22-FEB-81
         5 MARTIN     28-SEP-81

SQL>

Using NOT LIKE:

SQL> select * from emp where ename not like '_A%';

     EMPNO ENAME      HIREDATE
---------- ---------- ---------
         1 SMITH      17-DEC-80
         2 ALLEN      20-FEB-81
         4 JONES      02-APR-81

SQL>

To search for actual underscore or percent characters in a string, use the ESCAPE option.

For example, '%\%%' ESCAPE '\'

The character after the ESCAPE specifies the character used for escaping. In the example the backslash character (\) is used as the 'escape character'. The first % is treated as a wildcard. The second % is treated as an actual character to search for. The third % is treated as a wildcard.

CREATE TABLE EMP (EMPNO    NUMBER(4) NOT NULL,
                  ENAME    VARCHAR2(10),
                  HIREDATE DATE);

INSERT INTO EMP VALUES (1, 'S%MITH',TO_DATE('17-DEC-1980', 'DD-MON-YYYY'));
INSERT INTO EMP VALUES (2, 'ALLEN', TO_DATE('20-FEB-1981', 'DD-MON-YYYY'));
INSERT INTO EMP VALUES (3, 'WARD',  TO_DATE('22-FEB-1981', 'DD-MON-YYYY'));
INSERT INTO EMP VALUES (4, 'JONES', TO_DATE('2-APR-1981',  'DD-MON-YYYY'));
INSERT INTO EMP VALUES (5, 'MARTIN',TO_DATE('28-SEP-1981', 'DD-MON-YYYY'));

SQL> SELECT ename
  2  FROM emp WHERE ename LIKE '%\%%' ESCAPE '\';

ENAME
----------
S%MITH

SQL>