I created this table called LOCATION by doing this:
CREATE TABLE LOCATION( POSTCODE VARCHAR(10) PRIMARY KEY, STREET_NAME VARCHAR(20), CITY VARCHAR(20));
INSERT INTO LOCATION VALUES(PQ95VM,'HAPPY_STREET','FRANCE');
the above mentioned code is not correct because your first parameter POSTCODE is of type VARCHAR(10). you should have used ' '.
VARCHAR(10)
' '
try INSERT INTO LOCATION VALUES('PQ95VM','HAPPY_STREET','FRANCE');
INSERT INTO LOCATION VALUES('PQ95VM','HAPPY_STREET','FRANCE');