oracle中=>是什么意思呢？

Question

declare
type emp_record is record(f_name employees.first_name%type,h_date employees.hire_date%type);
v_emp_record emp_record;
cursor c3(dept_id number,j_id varchar2) return emp_record
is
select first_name,hire_date from employees where department_id=dept_id and job_id=j_id;
begin
open c3(j_id=>'AD_VP',dept_id=>90);
loop
fetch c3 into v_emp_record;
if c3%found then
dbms_output.put_line(v_emp_record.f_name||'的雇用日期是：'||v_emp_record.h_date);
else
dbms_output.put_line('已经处理完结果集');
exit;
end if;
end loop;
close c3;
end;

Answer 1

=> 是 Oracle 中调用 存储过程的时候, 指定 参数名进行调用.
一般是， 某些参数有默认值的时候，你需要跳过某些参数来进行调用。
下面是具体的例子。
参数的默认值
SQL> CREATE OR REPLACE PROCEDURE HelloWorld3 (
2 p_user_name VARCHAR2,
3 p_val1 VARCHAR2 DEFAULT ' Good Moning,',
4 p_val2 VARCHAR2 DEFAULT ' Nice to Meet you'
5 ) AS
6 BEGIN
7 dbms_output.put_line('Hello ' || p_user_name || p_val1 || p_val2 || '!'
);
8 END HelloWorld3;
9 /
Procedure created.
SQL> BEGIN
2 HelloWorld3('Edward');
3 HelloWorld3('Edward', ' Good Night,');
4 HelloWorld3('Edward', ' Good Night,', 'Bye');
5 END;
6 /
Hello Edward Good Moning, Nice to Meet you!
Hello Edward Good Night, Nice to Meet you!
Hello Edward Good Night,Bye!
PL/SQL procedure successfully completed.
指定参数名称调用
此部分使用 “参数默认值”那一小节的存储过程。
用于说明当最后2个参数是有默认的时候，如何跳过中间那个。
SQL> BEGIN
2 HelloWorld3('Edward');
3 HelloWorld3('Edward', p_val1 => ' Good Night,');
4 HelloWorld3('Edward', p_val1 => ' Good Night,', p_val2 => 'Bye');
5 HelloWorld3('Edward', p_val2 => ' HeiHei ');
6 END;
7 /
Hello Edward Good Moning, Nice to Meet you!
Hello Edward Good Night, Nice to Meet you!
Hello Edward Good Night,Bye!
Hello Edward Good Moning, HeiHei !
PL/SQL procedure successfully completed.