1Z0-051 QUESTION 4 单行函数Single-Row Functions

QUESTION 4
Which two statements are true regarding single row functions? (Choose two.)
A. They a ccept only a single argument.
B. They c an be nested only to two levels.
C. Arguments can only be column values or constants.
D. They a lways return a single result row for every row of a queried table.

E. They c an return a data type value different from the one that is referenced.

答案：DE

解析：参照Orcacle官方文档关于Single-Row Functions：

http://docs.oracle.com/cd/E11882_01/server.112/e26088/functions002.htm#SQLRF51178

摘要如下：

A选项，单行函数可以接收多个变量，如convert

B选项，单行函数可以被嵌套多级，如convert+to_char

C选项，参数还可以是变量和表达式

D选项完全和其中的描述一样

Single-row functions return a single result row for every row of a queried table or view. These functions can appear in select lists, WHERE clauses, START WITH and CONNECT BY clauses, and HAVING clauses.

单行函数返回一个结果行用于查询的表或视图的每一行。这些函数可以出现在select 结果清单，where语句，startup with 和connect by语句，和HAVING子句中。

E选项可以返回和原来不一样的数据类型，像Conversion functions convert a value from one data type to another。