Oracle null值

Question

有人可以在oracle db中解释下面查询的功能,为什么不返回最后一个空行.还请在空值的情况下解释我的功能.

Table Store_Information
store_name    Sales  Date
Los Angeles   $1500  Jan-05-1999
San Diego      $250  Jan-07-1999
San Francisco  $300  Jan-08-1999
Boston         $700  Jan-08-1999
(null)         $600  Jan-10-1999


SELECT *
FROM scott.Store_Information
WHERE store_name IN (null)

STORE_NAME           SALES                DATE                      
-------------------- -------------------- ------------------------- 

0 rows selected

Answer 1

SELECT *
FROM scott.Store_Information
WHERE store_name IS null;

NULL不能与其他(实际)值"比较".因此你必须使用IS NULL或IS NOT NULL.

以下是关于此主题的一系列博客文章:http://momjian.us/main/blogs/pgblog/2012.html#December_26_2012