oracle - 以下情况下 PLS_INTEGER 和 INTEGER 之间的区别

Question

请看这两个场景:

案例 1:

DECLARE
p1 PLS_INTEGER := 2147483647;
p2 INTEGER := 1;
n NUMBER;
BEGIN
n := p1 + p2;
END;

PL/SQL procedure successfully completed.

案例二

DECLARE
p1 PLS_INTEGER := 2147483647;
p2 PLS_INTEGER := 1;
n NUMBER;
BEGIN
n := p1 + p2;
END;

Error at line 1
ORA-01426: numeric overflow
ORA-06512: at line 6

为什么 case 2 失败，即使我试图添加相同的数据类型而 case 1 执行成功？

Answer 1

PLS_INTEGER and BINARY_INTEGER Data Types 的文档 只说:

A calculation with two PLS_INTEGER values that overflows the PLS_INTEGER range raises an overflow exception, even if you assign the result to a NUMBER data type.

但它没有告诉您原因。我认为原因是 PLS_INTEGER 操作使用硬件算法，因此 Oracle 正确地在内部执行它，例如

n := CAST(p1 + p2 AS NUMBER);