Oracle游标学习笔记

游标按以下操作进行
parse 解析
bind 绑定
open 打开
execute 执行
fetch 回取
close 关闭

1.写自己第一个游标PL/SQL
declare
 cursor c_s is select * from user_tables;
begin
 open c_s; --打开游标
 close c_s;--关闭游标
end;

游标的4个属性 %found,%notfound,%rowcount,%isopen
1.%found  游标有记录则返回true否则false
declare
 cursor c_s is select * from user_tables;
 cc c_s%rowtype;
begin
 open c_s; --打开游标
 fetch c_s into cc;
 while c_s%found loop
  fetch c_s into cc;
 end loop;
 close c_s;--关闭游标
end;
 
2.%notfound 游标没记录则返回true否则false(个人感觉有点多余)
declare
 cursor c_s is select * from user_tables;
 cc c_s%rowtype;//游标变量
begin
 open c_s; --打开游标
 fetch c_s into cc;
 while c_s%found loop
  exit when c_s%notfound;
 end loop;
 close c_s;--关闭游标
end;

3.%rowcount 返回游标取回的记录数目
declare
 cursor c_s is select * from user_tables;
 cc c_s%rowtype;
begin
 open c_s; --打开游标
 fetch c_s into cc;
 while c_s%found loop
  dbms_output.put_line(c_s%rowcount);
 end loop;
 close c_s;--关闭游标
end;

4.%isopen  如果游标打开就返回true 否则false
declare
 cursor c_s is select * from user_tables;
begin
 if c_s%isopen then
  dbms_output.put_line('cursor is open');
 else
  open c_s; --打开游标
 end if;
 close c_s;--关闭游标
end;

游标参数
declare
 cursor c_s(cs_id number) is select * from admin id=cs_id;
begin
 open c_s(10); --打开带参数的游标
 close c_s;--关闭游标
end;

游标中的for update
declare
 cursor c_s is select id from admin
 for update of id //查询时锁定 id列
begin
 open c_s;
 commit;//提交释放锁  或者可以用 rollback
 close c_s;
end;

游标中的where cursor of
UPDATE table_name SET set_clause WHERE CURSOR OF cursor_name; //更新游标所指向的那条记录
DELETE FROM table_name WHERE CURSOR OF cursor_name; //删除游标所指向的那条记录

游标中的ref cursor类型
TYPE c_s IS REF CURSOR RETRUN table%rowtype; //这种形式为强类型 在声明的时候就定了为行类型
TYPE c_s IS REF CURSOR;//弱类型 不与记录的数据类型关联
例子:
declare
 TYPE c_s IS REF CURSOR RETRUN table%rowtype;
 TYPE c_s2 IS REF CURSOR;
 var_cs c_s;//声明为游标变量的类型
begin
 OPEN c_s FOR select * from admin;
 CLOSE c_s;
end;