显式和隐式游标的区别:
尽量使用隐式游标,避免编写附加的游标控制代码(声明,打开,获取,关闭),也不需要声明变量来保存从游标中获取的数据。
REF CURSOR游标:
动态游标,在运行的时候才能确定游标使用的查询。分类:
强类型(限制)REF CURSOR,规定返回类型
弱类型(非限制)REF CURSOR,不规定返回类型,可以获取任何结果集。
TYPE ref_cursor_name IS REF CURSOR [RETURN return_type]
Declare
Type refcur_t is ref cursor;
Type emp_refcur_t is ref cursor return employee%rowtype;
Begin
Null;
End;
/
强类型举例:
declare
--声明记录类型
type emp_job_rec is record(
employee_id number,
employee_name varchar2(50),
job_title varchar2(30)
);
--声明REF CURSOR,返回值为该记录类型
type emp_job_refcur_type is ref cursor
return emp_job_rec;
--定义REF CURSOR游标的变量
emp_refcur emp_job_refcur_type;
emp_job emp_job_rec;
begin
open emp_refcur for
select e.employee_id,
e.first_name || ‘ ’ ||e.last_name “employee_name”,
j.job_title
from employees e, jobs j
where e.job_id = j.job_id and rownum < 11 order by 1;
fetch emp_refcur into emp_job;
while emp_refcur%found loop
dbms_output.put_line(emp_job.employee_name || ‘’’s job is ’);
dbms_output.put_line(emp_job.job_title);
fetch emp_refcur into emp_job;
end loop;
end;
/
单独select
declare
l_empno emp.EMPLOYEE_ID%type;
-- l_ename emp.ename%type;
begin
select EMPLOYEE_ID
into l_empno
from emp;
--where rownum =1;
dbms_output.put_line(l_empno);
end;
/
使用INTO获取值,只能返回一行。
错误处理:
exception
when
…
when
…
end;
exception_expression包括:
1. 预定义表达式
2. 用户定义表达式
3. PRAGMA EXCEPTION_INIT
预定义
declare
l_dept departments%rowtype;
begin
l_dept.department_id:=100;
l_dept.department_name:=’HR’;
insert into departments(department_id, department_name)
values(l_dept.department_id, l_dept.department_name);
Exception
When DUP_VAL_ON_INDEX then
Dbms_output.put_line(‘heihei’);
end;
/
DUP_VAL_ON_INDEX 异常
Exception
When DUP_VAL_ON_INDEX then
Dbms_output.put_line…..
自定义:
declare
l_exc exception;
begin
…
raise l_exc;
exception
when l_exc then
…
end;
/