什么是游标
游标是一种PL/SQL控制结构可以对SQL语句进行显示控制便于对表的数据逐条进行处理
游标分类
显示游标: Declared and named by the programmer
隐式游标: Declared for all DML and PL/SQL SELECT statements
游标的属性
%FOUNDEvaluates to TRUE if the most recent SQL statement affects one or more rows
%NOTFOUND和%FOUND相反
%ISOPEN是一个布尔值如果游标打开则为TRUE 如果游标关闭则为FALSE对于隐式游标而言SQL%ISOPEN总是FALSE这是因为隐式游标在DML语句执行时打开结束时就立即关闭
%ROWCOUNTNumber of records affected by the most recent SQL statement
注意dbms_outputput_line();这个是不能打印boolean型的解决方法
if b then
dbms_outputput_line(b=true);
end if;
或者
declare
b boolean;
begin
b := true;
dbms_outputput_line((case when b then true else false end));
end;
对于null课先使用NVL（）或者decode()处理
显示游标:需要手动open和close
例如
DECLARE
CURSOR mycursor IS
SELECT * FROM dept;
myrecord dept%ROWTYPE;
BEGIN
OPEN mycursor;
FETCH mycursor INTO myrecord;
WHILE mycursor%FOUND LOOP
DBMS_OUTPUTPUT_LINE(myrecorddeptno|| ||myrecorddname|| ||myrecordloc);
FETCH mycursor INTO myrecord;
END LOOP;
CLOSE mycursor;
END;
注意在进行while循环前必须先有一个FETCHINTO操作否者%FOUND总是返 回false
带参数的游标
DECLARE
CURSOR mycursor(num varchar) IS
SELECT * FROM DEPT WHERE deptno=num;
myrecord dept%ROWTYPE;
BEGIN
OPEN mycursor();
LOOP
FETCH mycursor INTO myrecord;
EXIT WHEN mycursor%NOTFOUND;
DBMS_OUTPUTPUT_LINE(deptNum=||myrecorddeptno|| deptName=||myrecorddname);
END LOOP;
CLOSE mycursor;
END;
FOR循环操作游标
使用FOR循环读取游标时不需要显示申明变量用于接收结果也不需要手动打开和关闭游标例如
DECLARE
CURSOR mycursor(num varchar) IS
SELECT * FROM DEPT WHERE deptno=num;
BEGIN
FOR cur IN mycursor() LOOP
DBMS_OUTPUTPUT_LINE(deptNum=||curdeptno|| deptName=||curdname);
END LOOP;
END;
注意PL/SQL中参数只需要给出类型不需要给出长度或精度
当直接将游标的值读取到变量时变量的个数应与游标指向的结果集的列数相同例如结果集中有两个列那么使用FETCHINTO 时对应的变量个数也应该有两个
DECLARE
d_no number;
d_name varchar();
CURSOR mycursor(num varchar) IS
SELECT deptnodname FROM DEPT WHERE deptno=num;
BEGIN
OPEN mycursor();
FETCH mycursor INTO d_nod_name;
LOOP
DBMS_OUTPUTPUT_LINE(d_no|| ||d_name);
FETCH mycursor INTO d_nod_name;
EXIT WHEN mycursor%NOTFOUND;
END LOOP;
CLOSE mycursor;
END;
/
%ROWCOUNT初始值为null每当使用FETCHINTO从游标中取出一条数据后 ROWCOUNT的值加并不是标识结果集的行数
例如
DECLARE
d_name varchar();
CURSOR mycursor IS
SELECT dname FROM DEPT;
BEGIN
OPEN mycursor;
LOOP
FETCH mycursor INTO d_name;
EXIT WHEN mycursor%NOTFOUND;
DBMS_OUTPUTPUT_LINE(mycursor%ROWCOUNT);
END LOOP;
CLOSE mycursor;
END;
结果集中有行记录输出结果为
可更新数据的游标
要想在使用游标的同时修改数据需要在申明游标时加上FOR UPDATE关键字
例如
DECLARE
d_name VARCHAR();
CURSOR mycursor IS
SELECT dname FROM dept FOR UPDATE;
BEGIN
OPEN mycursor;
LOOP
FETCH mycursor INTO d_name;
EXIT WHEN mycursor%NOTFOUND;
UPDATE dept SET dname=RTRIM(dname_t) WHERE CURRENT OF mycursor;
END LOOP;
CLOSE mycursor;
END;
CURRENT OF+游标名获取游标当前所指向的行
RTRIM(dname_t)LTRIMRTRIM实现字符串过滤(不仅仅去除空格)
隐式游标不使用DECLARE显示申明的游标
例如
BEGIN
FOR cur IN(SELECT dname FROM dept) LOOP
DBMS_OUTPUTPUT_LINE(curdname);
END LOOP;
END;
含有参数的游标
declare
cursor cur_my (mv number) is select * from Person where no<mv;
begin
for tem in cur_my() loop
DBMS_OUTPUTput_line(name:||temname);
end loop;
end;
设置引用游标
declare
temp_row Person%rowtype;
type my_type is ref cursor;
cur_my my_type;
begin
open cur_my for select * from Person ;
loop
fetch cur_my into temp_row;
exit when cur_my%notfound;
DBMS_OUTPUTput_line(name:||temp_rowname);
end loop;
close cur_my;
end;
for loop循环游标
DECLARE
v_id Integer;
v_name varchar();
v_age Integer;
cursor cur_mycursor is select idnameage from Users;
BEGIN
for temp in cur_mycursor loop
v_id :=tempid;
v_name :=tempname;
v_age :=tempage;
dbms_outputput_line(id:||v_id||name:||v_name||age:||v_age);
end loop;
/**dbms_outputput_line(所有记录数||cur_mycursor%rowcount||条！);*/
END;
标准化loop循环游标
DECLARE
v_id Integer;
v_name varchar();
v_age Integer;
cursor cur_mycursors is select idnameage from Users;
BEGIN
OPEN cur_mycursors;
dbms_outputput_line(所有记录数||cur_mycursors%rowcount||条！);
LOOP
FETCH cur_mycursors INTO v_idv_namev_age;
dbms_outputput_line(id:||v_id||name:||v_name||age:||v_age);
IF cur_mycursors%NOTFOUND THEN
EXIT;
END IF;
END LOOP;
dbms_outputput_line(所有记录数||cur_mycursors%rowcount||条！);
CLOSE cur_mycursors;
END;
