varchar type not equals or null value : VARCHAR2 « SQL Data Types « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. SQL Data Types
3. VARCHAR2

SQL>
SQL>
SQL> CREATE TABLE publishers(
  2    pub_id   CHAR(3)     NOT NULL,
  3    pub_name VARCHAR(20) NOT NULL,
  4    city     VARCHAR(15) NOT NULL,
  5    state    CHAR(2)     NULL    ,
  6    country  VARCHAR(15) NOT NULL);

Table created.

SQL>
SQL> INSERT INTO publishers VALUES('P01','A','New York','NY','USA');

1 row created.

SQL> INSERT INTO publishers VALUES('P02','C','San Francisco','CA','USA');

1 row created.

SQL> INSERT INTO publishers VALUES('P03','S','Hamburg',NULL,'Germany');

1 row created.

SQL> INSERT INTO publishers VALUES('P04','T','Berkeley','CA','USA');

1 row created.

SQL>
SQL> SELECT pub_id, city, state, country
  2    FROM publishers
  3    WHERE state <> 'CA'
  4       OR state IS NULL;

PUB CITY            ST COUNTRY
--- --------------- -- ---------------
P01 New York        NY USA
P03 Hamburg            Germany

SQL>
SQL>
SQL> drop table publishers;

Table dropped.

SQL>
SQL>