IS NOT NULL 命令用于测试非空值(非空值)。
IS NOT NULL
下面的 SQL 列出了所有 "Address" 字段有值(非空值)的客户信息:
SELECT CustomerName, ContactName, AddressFROM CustomersWHERE Address IS NOT NULL;
SELECT CustomerName, ContactName, Address
FROM Customers
WHERE Address IS NOT NULL;