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What Is NULL
What Is NULL? - Oracle DBA FAQ - Understanding SQL Basics
✍: FYIcenter.com
NULL is a special value representing "no value" in all data types. NULL can be used on in operations like other values. But most opertations has special rules when NULL is involved. The tutorial exercise below shows you some examples:
SET NULL 'NULL'; -- Make sure NULL is displayed SELECT NULL FROM DUAL; N - N U L L SELECT NULL + NULL FROM DUAL; NULL+NULL ---------- NULL SELECT NULL + 7 FROM DUAL; NULL+7 ---------- NULL SELECT NULL * 7 FROM DUAL; NULL*7 ---------- NULL SELECT NULL || 'A' FROM DUAL; N - A SELECT NULL + SYSDATE FROM DUAL; NULL+SYSD --------- NULL
2007-04-23, 4809👍, 0💬
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