ORACLE STUDY NOTES 04

Posted 2020-08-25

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【JSU】LJDragon‘s Oracle course notes In the first semester, junior year

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PL/SQL游标(declare .. begin .. end)

--游标：指向查询结果集的指针，指针指向哪一行，提取的就是哪一行的数据

--PLSQL的游标默认指向结果集的第1行

--显示游标的四大步骤：

1.定义游标 cursor 游标变量名 is 查询语句;

2.打开游标 open 游标变量名;(可以重复打开)

3.提取游标 fetch 游标变量名 into 变量名;

4.关闭游标 close 游标变量名;

--游标的四大属性：

1.游标变量名%FOUND 布尔型属性，当最近一次读记录时成功返回,则值为TRUE；

2.游标变量名%NOTFOUND 和%found相反

3.游标变量名%ISOPEN 布尔型属性，当游标已打开时返回 TRUE；

4.游标变量名%ROWCOUNT 数字型属性，返回已从游标中读取的记录数

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--查询输出10号部门的所有员工(编号，姓名，工资)

1. declare
2. ???????cursor emp_cursor is --1.定义游标
3. ???????select empno,ename,sal from emp where deptno = 10;
4. ???????v_empno emp.empno%type;
5. ???????v_ename emp.ename%type;
6. ???????v_sal emp.sal%type;
7. begin
8. ???????open emp_cursor; --2.打开游标
9. ???????fetch emp_cursor into v_empno,v_ename,v_sal; --3.提取游标
10. ????????dbms_output.put_line(emp_cursor%ROWCOUNT);
11. ???????fetch emp_cursor into v_empno,v_ename,v_sal;
12. ???????fetch emp_cursor into v_empno,v_ename,v_sal;
13. ???????dbms_output.put_line(emp_cursor%ROWCOUNT);
14. ?
15. ????????if emp_cursor%notfound then
16. ??????????dbms_output.put_line(‘true‘);
17. ???????else
18. ?????????dbms_output.put_line(‘false‘);
19. ???????end if;
20. ???????dbms_output.put_line(v_empno||‘,‘||v_ename||‘,‘||v_sal);
21. ???????close emp_cursor; --4.关闭游标
22. end;

--方法2：loop循环

1. declare
2. ???????cursor emp_cursor is
3. ???????select empno,ename,sal from emp where deptno = 10;
4. ???????v_empno emp.empno%type; --参照表的列的数据类型 表名.列名%type
5. ???????v_ename emp.ename%type;
6. ???????v_sal emp.sal%type;
7. begin
8. ???????open emp_cursor;
9. ??????loop
10. ????????????fetch emp_cursor into v_empno,v_ename,v_sal;
11. ????????????exit when emp_cursor%notfound;
12. ????????????dbms_output.put_line(v_empno||‘,‘||v_ename||‘,‘||v_sal);
13. ??????end loop;
14. ??????close emp_cursor;
15. end;

--方法3：--while loop循环

1. declare
2. ???????cursor emp_cursor is
3. ???????select empno,ename,sal from emp where deptno = 10;
4. ???????v_empno emp.empno%type;
5. ???????v_ename emp.ename%type;
6. ???????v_sal emp.sal%type;
7. begin
8. ???????open emp_cursor;
9. ???????fetch emp_cursor into v_empno,v_ename,v_sal;
10. ???????while emp_cursor%found loop
11. ????????????dbms_output.put_line(v_empno||‘,‘||v_ename||‘,‘||v_sal);
12. ????????????fetch emp_cursor into v_empno,v_ename,v_sal;
13. ???????end loop;
14. ??????close emp_cursor;
15. end;

--改成参照类型（？）

1. declare
2. ???????cursor emp_cursor is
3. ???????select * from emp where deptno = 10;
4. ???????e emp%rowtype;
5. begin
6. ???????open emp_cursor;
7. ??????loop
8. ????????????fetch emp_cursor into e;
9. ????????????exit when emp_cursor%notfound;
10. ????????????dbms_output.put_line(e.empno||‘,‘||e.ename||‘,‘||e.sal);
11. ??????end loop;
12. ??????close emp_cursor;
13. end;

--游标提取的值赋给表类型(动态数组)

1. declare
2. ???????cursor emp_cursor is
3. ???????select * from emp;
4. ???????type emp_table_type is table of emp%rowtype
5. ???????index by binary_integer;
6. ?
7. ???????e emp_table_type;
8. begin
9. ??????open emp_cursor;
10. ????????????fetch emp_cursor bulk collect into e limit 5;--限制取的条数
11. ??????close emp_cursor;
12. ?
13. ??????for i in 1 .. e.count loop
14. ??????????dbms_output.put_line(e(i).ename);
15. ??????end loop;
16. end;

--循环取出所有的记录

1. declare
2. ???????cursor emp_cursor is
3. ???????select * from emp;
4. ???????type emp_table_type is table of emp%rowtype
5. ???????index by binary_integer;
6. ?
7. ???????e emp_table_type;
8. begin
9. ??????open emp_cursor;
10. ??????loop
11. ????????????fetch emp_cursor bulk collect into e limit 5;--限制取的条数
12. ???????????????for i in 1 .. e.count loop
13. ???????????????????dbms_output.put_line(e(i).ename);
14. ???????????????end loop;
15. ????????????exit when emp_cursor%notfound;
16. ??????end loop;
17. ??????close emp_cursor;
18. end;

--带参数游标,根据部门编号查询员工信息

1. declare
2. ???????cursor emp_cursor(p_deptno emp.deptno%type) is
3. ???????select * from emp where deptno = p_deptno;
4. ???????e emp%rowtype;
5. begin
6. ???????open emp_cursor(10);
7. ??????loop
8. ????????????fetch emp_cursor into e;
9. ????????????exit when emp_cursor%notfound;
10. ????????????dbms_output.put_line(e.empno||‘,‘||e.ename||‘,‘||e.sal);
11. ??????end loop;
12. ??????close emp_cursor;
13. ??????dbms_output.put_line(‘-----------------‘);
14. ???????open emp_cursor(20);
15. ??????loop
16. ????????????fetch emp_cursor into e;
17. ????????????exit when emp_cursor%notfound;
18. ????????????dbms_output.put_line(e.empno||‘,‘||e.ename||‘,‘||e.sal);
19. ??????end loop;
20. ??????close emp_cursor;
21. end;

--游标for循环

1. declare
2. ???????cursor emp_cursor is select * from emp ;
3. begin
4. ???????for e in emp_cursor loop
5. ?????????dbms_output.put_line(e.ename);
6. ???????end loop;
7. end;

--最精简版

1. begin
2. ???????for e in ( select * from emp) loop
3. ?????????dbms_output.put_line(e.ename);
4. ???????end loop;
5. end;

--根据部门表循环输出员工信息

--部门编号:10，部门名称

--员工编号:xxx ,姓名:xxx，职位:xxx，入职日期:xxx

--员工编号:xxx ,姓名:xxx，职位:xxx，入职日期:xxx

--员工编号:xxx ,姓名:xxx，职位:xxx，入职日期:xxx

--部门编号:20，部门名称

--员工编号:xxx ,姓名:xxx，职位:xxx，入职日期:xxx

--员工编号:xxx ,姓名:xxx，职位:xxx，入职日期:xxx

--员工编号:xxx ,姓名:xxx，职位:xxx，入职日期:xxx

--游标for循环带参数写法

1. declare
2. ???????cursor dept_cursor is
3. ???????select * from dept;
4. ?
5. ???????cursor emp_cursor(v_deptno emp.deptno%type) is
6. ???????select * from emp where deptno = v_deptno;
7. begin
8. ???????for d in dept_cursor loop
9. ??????????dbms_output.put_line(d.deptno||‘,‘||d.dname);
10. ??????????for e in emp_cursor(d.deptno) loop
11. ????????????dbms_output.put_line(‘ ‘||e.job||‘,‘||e.ename||‘,‘||e.hiredate);
12. ????????????end loop;
13. ???????end loop;
14. end;

--精简写法

1. begin
2. ???????for d in (select * from dept) loop
3. dbms_output.put_line(d.deptno||‘,‘||d.dname);
4. ??????????for e in (select * from emp where deptno = d.deptno) loop
5. dbms_output.put_line(‘ ‘||e.job||‘,‘||e.ename||‘,‘||e.hiredate);
6. ??????????end loop;
7. ???????end loop;
8. end;

--隐式游标

隐式游标：固定名称SQL

游标四个属性：

SQL%FOUND：如果操作有影响的行，就为TRUE，否则为FALSE

SQL%NOTFOUND：求反

SQL%ISOPEN：在隐式游标中，取值永远为FALSE

SQL%ROWCOUNT：操作影响的行数

1.在事务提交之前获取游标属性;

2.只取最近的一条DML操作状态;

1. begin
2. ???????update emp set sal = sal + 10 where deptno = 20;
3. ???????--delete emp where 1=2;
4. ???????if SQL%FOUND THEN
5. ?????????dbms_output.put_line(‘TRUE‘);
6. ???????ELSE
7. ?????????dbms_output.put_line(‘FALSE‘);
8. ???????END IF;
9. ???????dbms_output.put_line(SQL%ROWCOUNT);
10. ???????commit;
11. end;

--游标更新（current of 游标变量名）

--更改所有员工工资<1000,加1000；

1. declare
2. ???????cursor emp_c is
3. ???????select * from emp for update;
4. begin
5. ???????for e in emp_c loop
6. ?????????if e.sal <3000 then
7. ????????????update emp set sal = sal + 1000 where current of emp_c;
8. ?????????end if;
9. ???????end loop;
10. ??????-- dbms_output.put_line(SQL%ROWCOUNT);
11. end;

--动态游标

--根据用户的输入选择输出不同的表记录

--E,查询输出emp的姓名

--D,查询输出dept的部门名称

1. DECLARE
2. ???????v_cmd CHAR(1) := ‘&input‘;
3. ???????v_name VARCHAR2(50);
4. ?
5. ???????--声明自定义的游标变量类型
6. ???????--TYPE c_type IS REF CURSOR;
7. ???????--声明游标变量
8. ????????--c c_type;
9. ?
10. ???????c SYS_REFCURSOR;--代替TYPE c_type IS REF CURSOR
11. BEGIN
12. ???????IF v_cmd=‘E‘ THEN
13. ??????????dbms_output.put_line(‘员工姓名‘);
14. ??????????OPEN c FOR SELECT ename FROM emp;
15. ???????ELSIF v_cmd=‘D‘ THEN
16. ??????????dbms_output.put_line(‘部门名称‘);
17. ??????????OPEN c FOR SELECT dname FROM dept;
18. ???????ELSE
19. ??????????dbms_output.put_line(‘输入无效‘);
20. ??????????RETURN;
21. ???????END IF;
22. ?
23. ???????LOOP
24. ???????????FETCH c INTO v_name;
25. ???????????EXIT WHEN c%NOTFOUND;
26. ???????????dbms_output.put_line(v_name);
27. ???????END LOOP;
28. ?
29. ???????CLOSE c;
30. END;

【JSU】LJDragon‘s Oracle course over in 5th.