PL_SQL基础--续四

游标---PL_SQL里面的重点****:
declare ---loop循环
cursor c is --声明一个游标
select * from emp;
v_emp c%rowtype; --声明一条记录
begin
open c; --打开游标
loop
fetch c into v_emp; --截取数据。
exit when (c%notfound); --判断游标是否到终点
dbms_output.put_line(v_emp.ename);
end loop;
close c; --关闭游标
end;

--while循环
declare
cursor c is
select * from emp;
v_emp emp%rowtype;
begin
open c;
fetch c into v_emp;
while (c%found) loop
dbms_output.put_line(v_emp.ename);
fetch c into v_emp;
end loop;
close c;
end;

--for循环，不容易出错，用得最多。
declare
cursor c is
select * from emp;
begin
for v_emp in c loop --不需要定义v_emp,自动打开，关闭c.自动fetch数据。
dbms_output.put_line(v_emp.ename);
end loop;
end;

---带参数的游标
declare
cursor c(v_deptno emp.deptno%type,v_job emp.job%type)
is
select ename,sal from emp where deptno = v_deptno and job = v_job;
begin
for v_temp in c(30,'CLERK') loop
dbms_output.put_line(v_temp.ename);
end loop;
end;

---可更新的游标
declare
cursor c
is
select * from emp2 for update; --跟上for update表示可更新游标。
begin
for v_temp in c loop
if(v_temp.sal < 2000) then
update emp2 set sal = sal * 2 where current of c; ---更新游标所指的当前记录
elsif (v_temp.sal = 5000) then
delete from emp2 where current of c; ---where current of c.
end if;
end loop ;
end;