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Oracle HowTo:如何使用Oracle的Decode函数进行多值判断
作者：eygle |【转载时请以超链接形式标明文章出处和作者信息及本声明】链接：http://www.eygle.com/archives/2005/10/oracle_howto_use_decode_function.html
Decode函数的语法结构如下:
decode (expression, search_1, result_1) decode (expression, search_1, result_1, search_2, result_2) decode (expression, search_1, result_1, search_2, result_2, ...., search_n, result_n) decode (expression, search_1, result_1, default) decode (expression, search_1, result_1, search_2, result_2, default) decode (expression, search_1, result_1, search_2, result_2, ...., search_n, result_n, default) |
decode函数比较表达式和搜索字，如果匹配，返回结果；如果不匹配，返回default值；如果未定义default值，则返回空值。
以下是一个简单测试，用于说明Decode函数的用法:
SQL> create table t as select username,default_tablespace,lock_date from dba_users; Table created. SQL> select * from t; USERNAME DEFAULT_TABLESPACE LOCK_DATE ------------------------------ ------------------------------ --------- SYS SYSTEM SYSTEM SYSTEM OUTLN SYSTEM CSMIG SYSTEM SCOTT SYSTEM EYGLE USERS DBSNMP SYSTEM WMSYS SYSTEM 20-OCT-04 8 rows selected. SQL> select username,decode(lock_date,null,'unlocked','locked') status from t; USERNAME STATUS ------------------------------ -------- SYS unlocked SYSTEM unlocked OUTLN unlocked CSMIG unlocked SCOTT unlocked EYGLE unlocked DBSNMP unlocked WMSYS locked 8 rows selected. SQL> select username,decode(lock_date,null,'unlocked') status from t; USERNAME STATUS ------------------------------ -------- SYS unlocked SYSTEM unlocked OUTLN unlocked CSMIG unlocked SCOTT unlocked EYGLE unlocked DBSNMP unlocked WMSYS 8 rows selected. |
历史上的今天...
>> 2004-10-05文章:
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这篇 【Oracle HowTo:如何使用Oracle的Decode函数进行多值判断】来自 eygle.com | CSDN网摘| del.icio.us|Google订阅 | 鲜果订阅 | 抓虾订阅
By eygle on 2005-10-05 12:06 | Comments (3) | Posted to HowTo | Edit |
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留言 (3)
谢谢
Posted by: 1 at February 2, 2009 2:55 PM
还好 不错
Posted by: cloud at September 11, 2009 10:46 AM
还好 不错
Posted by: cloud at September 11, 2009 10:47 AM