Oracle系统函数、自定义函数、关键字，收集一些在工作中常用的Oracle知识点，不断的更新，不断的积累，就当作自己的记事本吧。
Oracle系统函数、自定义函数、关键字
[日期：2012-06-16] 来源：Linux社区 作者：baolong47 [字体：]
题记：收集一些在工作中常用的Oracle知识点，不断的更新，不断的积累，就当作自己的记事本吧。
一些关键字
1 IS NOT NULL，，判断字段否为空
2CASE WHEN．．． THEN ．．． ELSE ．．． END ，条件语句
3EXITS , NOT EXITS, 判断是否存在，通常放到WHERE 的后面
一些系统函数
1. TO_CHAR()
显示 ： 2012-06-15 10:11:45
2. TO_DATE() 转为为某种格式的时间
一些自定义函数
1. 写一个工作用到的函数CHECK_DEMAND_IS_NOTICE，该函数需传入一个NUMBER类型的数据，结果返回一个 VARCHAR2的类型数据
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