Form compound conditions

To connect two or more comparison conditions, or Boolean expressions, use the logical operators AND, OR, and NOT. A Boolean expression evaluates as true or false or, if NULL values are involved, as unknown.

In the following query, the operator AND combines two comparison expressions in the WHERE clause.

Figure 1. Query

SELECT order_num, customer_num, po_num, ship_date
   FROM orders
   WHERE paid_date IS NULL
      AND ship_date IS NOT NULL
   ORDER BY customer_num;

The query returns all rows that have NULL paid_date or a NOT NULL ship_date.

Figure 2. Query result

order_num customer_num po_num     ship_date  

     1004          106 8006       05/30/1998
     1007          117 278693     06/05/1998
     1012          117 278701     06/29/1998
     1017          120 DM354331   07/13/1998