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Oracle DB 嵌套函数

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Jun 07, 2016 pm 05:32 PM

oracle function

单行函数可以嵌套到任意深度。嵌套函数的计算顺序是从最内层到最外层。下面的一些示例显示这类函数的灵活性。

示例显示部门60 中的雇员的姓氏。该SQL 语句的计算涉及以下三个步骤：

1.内部函数检索姓氏的前8 个字符。

Result1 = SUBSTR (LAST_NAME, 1, 8)

2.外层函数将结果与_US连接在一起。

Result2 = CONCAT(Result1, '_US')

3.最外层函数将结果转换为大写。

因为没有给出列别名，所以整个表达式就成为列标题。

示例：

显示距聘用日期六个月后的下一个星期五的日期。按聘用日期对结果排列。

Next 6 Month Review

-------------------------------------------------------------------------------------

Friday, July 20th, 2001

Friday, December 13th, 2002

，

Statement

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