为什么Oracle plsql varchar2变量需要大小但参数不需要大小? [英] Why does an oracle plsql varchar2 variable need a size but a parameter does not?

问题描述

假设您执行以下步骤:

PROCEDURE f (param VARCHAR2)
IS 
   var VARCHAR2(10);
BEGIN
   var := 'hi';
END f;

我想了解为什么var需要指定的长度，但param不需要.我很难在oracle文档中找到有关此信息.

I would like to understand why var needs a length specified, but param does not. I'm having a hard time finding information about this in the oracle docs.

推荐答案

"Oracle数据库从调用过程的环境中得出参数的长度，精度和小数位数."

"Oracle Database derives the length, precision, and scale of an argument from the environment from which the procedure is called."

请查看此相关问题.

参考:Oracle®数据库SQL参考10g第2版( 10.2) 请查看语义/参数/数据类型.

Reference: Oracle® Database SQL Reference 10g Release 2 (10.2) Please look under semantics / argument / datatype.

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