Conventional SQL identifiers must:

• Begin with an uppercase or lowercase letter
• Contain only letters (A-Z), digits (0-9), or the underscore character ( _ )
• Not be reserved words, such as CREATE or DROP
• Use ASCII characters only

SQL does not distinguish between uppercase and lowercase letters in SQL identifiers. It converts all names specified as conventional identifiers to uppercase, but statements can refer to the names in mixed case.

SELECT CustNum, COUNT(*)
     FROM Order
     WHERE OrderDate < TO_DATE ('3/31/2004')
     GROUP BY CustNum
     HAVING COUNT (*) > 10 ;