oracle复习笔记之PL/SQL程序所要了解的知识点

编程学习 2021-07-05 16:08www.dzhlxh.cn编程入门
本文主要是前篇文章的续篇,主要来复习PL/SQL的基本语法、记录类型、流程控制、游标的使用、异常处理机制、存储函数/存储过程、触发器。好记性不如烂笔头,古人诚不欺我~

复习内容:

PL/SQL的基本语法、记录类型、流程控制、游标的使用、

异常处理机制、存储函数/存储过程、触发器。

为方便大家跟着我的笔记练习,为此提供数据库表文件给大家下载:

为了要有输出的结果,在写PL/SQL程序前都在先运行这一句:
set serveroutput on
结构:
declare
--声明变量、类型、游标
begin
--程序的执行部分(类似于java里的main()方法)
exception
--针对begin块中出现的异常,提供处理的机制
--when...then...
--when...then...
end;
举例1:

declare
  v_sal number(10); (注意每句话后面别忘记了分号,跟java中的一样)
begin
  select salary into v_sal from employees where employee_id = 100;
  dbms_output.put_line(v_sal);
end;

举例2:

declare
  v_sal number(10); (注意,这里声明的空间大小不能比原表中的小)
  v_email varchar2(20);
  v_hire_date date;
begin
  select salary,email,hire_date into v_sal,v_email,v_hire_date from employees where employee_id = 
100;
  dbms_output.put_line(v_sal||','||v_email||','||v_hire_date);
end;
或者:
declare
  v_sal employees.salary%type;
  v_email employees.email%type;
  v_hire_date employees.hire_date%type;
begin
  select salary,email,hire_date into v_sal,v_email,v_hire_date from employees where employee_id = 
100;
  dbms_output.put_line(v_sal||','||v_email||','||v_hire_date);
end;

记录:

declare 
  type emp_record is record(
   v_sal employees.salary%type,
   v_email employees.email%type,
   v_hire_date employees.hire_date%type
  );
  v_emp_record emp_record;
begin
  select salary,email,hire_date into v_emp_record from employees where employee_id = 100;
  dbms_output.put_line(v_emp_record.v_sal||','||v_emp_record.v_email||','|| 
  v_emp_record.v_hire_date);
end;

1、pl/sql基本的语法格式
2、记录类型 type ... is ...record(,,,);
3、流程控制:
3.1 条件判断(两种)
方式一: if ... then elseif then ... else ... end if;
方式二: case ... when ... then ...end;
3.2 循环结构(三种)
方式一:loop ... exit when ... end loop;
方式二:while ... loop ... end loop;
方式三:for i in ... loop ... end loop;
3.3 goto、exit
4.游标的使用(类似于java中的Iterator)
5.异常的处理

6.会写一个存储函数(有返回值)、存储过程(没有返回值
7.会写一个触发器

复习记录类型:

declare
type emp_record is record(
  -- v_emp_id employees.employee_id%type,
  -- v_sal employees.salary%type
  v_emp_id number(10) := 120,
  v_sal number(10,2) :=12000
);
  v_emp_record emp_record;
begin
  -- select employee_id,salary into v_emp_record from employees where employee_id = 123;
  dbms_output.put_line('employee_id:'||v_emp_record.v_emp_id||' '||'salary:'|| 
  v_emp_record.v_sal);
end;

也可以升级一下,要是想对表的所有列都输出,则:(须注意输出的列名要跟表中的列名要一样)

declare
  v_emp_record employees%rowtype;
begin
  select * into v_emp_record from employees where employee_id = 123;
  dbms_output.put_line('employee_id:'||v_emp_record.employee_id||' '||'salary:'|| 
  v_emp_record.salary);
end;
使用记录来执行update操作:
declare 
  v_emp_id number(10);
begin
  v_emp_id :=123;
  update employees
  set salary = salary + 100
  where employee_id = v_emp_id;
  dbms_output.put_line('执行成功!~~');
end;

流程控制:
查询150号员工的工资,若其工资大于或等于10000 则打印‘salary >= 10000';
若在5000到10000之间,则打印‘5000 <= salary <10000';否则打印‘salary < 5000'

declare 
  v_sal employees.salary%type;
begin
  select salary into v_sal from employees where employee_id =150;
  if v_sal >= 10000 then dbms_output.put_line('salary >= 10000');
  elsif v_sal > 5000 then dbms_output.put_line('10000 > salary >= 5000');
  else dbms_output.put_line('salary < 5000');
  end if;
  dbms_output.put_line('salary:'||v_sal);
end;
利用case ... when ... then ... when ...then ... else ... end实现上题;
declare 
  v_sal employees.salary%type;
  v_temp varchar2(20);
begin
  select salary into v_sal from employees where employee_id =150;
  v_temp :=
  case trunc(v_sal/5000) when 0 then 'salary < 5000'
                  when 1 then '5000 <= salary < 10000'
                  else 'salary >= 10000'
                  end;
  dbms_output.put_line('salary:'||v_sal||' '||v_temp);
end;


查询出122号员工的job_id,若其值为 ‘IT_PROG', 则打印‘GRADE:A'
                                                ‘AC_MGT', 则打印‘GRADE:B'
                                                ‘AC_ACCOUNT', 则打印‘GRADE:B'
                                                 否则打印‘GRADE:D'

declare 
  v_job_id employees.job_id%type;
  v_temp varchar2(20);
begin
  select job_id into v_job_id from employees where employee_id =122;
  v_temp :=
  case v_job_id when 'IT_PROG' then 'A'
            when 'AC_MGT' then 'B'
            when 'AC_ACCOUNT' then 'C'
            else 'D'
            end;
  dbms_output.put_line('job_id:'||v_job_id||' '||v_temp);
end;

使用循环语句打印:1-100

declare
  v_i number(5) :=1;

begin
  loop
  dbms_output.put_line(v_i);
  exit when v_i >=100;
  v_i := v_i + 1;
  end loop;
end;
使用while实现:
declare
  v_i number(5) :=1;
begin
  while v_i <= 100 loop
   dbms_output.put_line(v_i);
   v_i := v_i + 1;
  end loop;
end;
使用for...in...loop...end loop;实现:
begin
  for c in 1..100 loop
   dbms_output.put_line(c);
  end loop;
end;


输出2-100之间的质数

declare
  v_i number(3):= 2;
  v_j number(3):= 2;
  v_flag number(1):= 1;
begin 
  while v_i<=100 loop
   while v_j<=sqrt(v_i) loop
    if mod(v_i,v_j)=0 then v_flag:=0;
    end if;
    v_j:= v_j+1;
   end loop;
  if v_flag = 1 then dbms_output.put_line(v_i);
  end if;
  v_j :=2;
  v_i := v_i + 1;
  v_flag := 1;
  end loop;
end;

利用for循环实现输出2-100之间的质数:

declare
  v_flag number(1):= 1;
begin 
  for v_i in 2..100 loop
   for v_j in 2..sqrt(v_i) loop
    if mod(v_i,v_j)=0 then v_flag:=0;
    end if;
   end loop;
   if v_flag=1 then dbms_output.put_line(v_i);
   end if;
   v_flag := 1;
  end loop;
end; 

可以用goto改进一下:

declare
  v_flag number(1):= 1;
begin 
  for v_i in 2..100 loop
    for v_j in 2..sqrt(v_i) loop
     if mod(v_i,v_j)=0 then v_flag:=0;
     goto label;
     end if;
   end loop;
   <<label>>
   if v_flag=1 then dbms_output.put_line(v_i);
   end if;
   v_flag := 1;
  end loop;
end; 

打印1-100的自然数,当打印到50时,跳出循环 ,输出‘打印结束':

begin 
  for i in 1..100 loop
   if i=50 then goto label;
   end if;
  dbms_output.put_line(i);
  end loop;
<<label>>
  dbms_output.put_line('打印结束');
end;
或者:
begin 
  for i in 1..100 loop
   if i=50 then dbms_output.put_line('打印结束');
   exit;
   end if;
  dbms_output.put_line(i);
  end loop;
end;

 

游标:
打印出80部门的所有的员工的工资:salary:XXX
declare
v_sal employees.salary%type;
--定义游标
cursor emp_sal_cursor is select salary from employees where department_id = 80;
begin
--打开游标
open emp_sal_cursor;
--提取游标
fetch emp_sal_cursor into v_sal;
while emp_sal_cursor%found loop
dbms_output.put_line('salary:'||v_sal);
fetch emp_sal_cursor into v_sal;
end loop;
--关闭游标
close emp_sal_cursor;
end;
可以进行优化如下:

declare
v_empid employees.employee_id%type;
v_lastName employees.last_name%type;
v_sal employees.salary%type;
cursor emp_sal_cursor is select employee_id,last_name,salary from employees where 
department_id = 80;
begin 
open emp_sal_cursor;
fetch emp_sal_cursor into v_empid,v_lastName,v_sal;
while emp_sal_cursor%found loop
dbms_output.put_line('employee_id:'||v_empid||', '||'last_name:'||v_lastName||', 
'||'salary:'||v_sal);
fetch emp_sal_cursor into v_empid,v_lastName,v_sal;
end loop;
close emp_sal_cursor;
end;

或者使用记录再优化一下:

declare
type emp_record is record(
v_empid employees.employee_id%type,
v_lastName employees.last_name%type,
v_sal employees.salary%type
);
v_emp_record emp_record;
cursor emp_sal_cursor is select employee_id,last_name,salary from employees where 
department_id = 80;
begin 
open emp_sal_cursor;
fetch emp_sal_cursor into v_emp_record;
while emp_sal_cursor%found loop
dbms_output.put_line('employee_id:'||v_emp_record.v_empid||', '||'last_name:'|| 
v_emp_record.v_lastName||', '||'salary:'||v_emp_record.v_sal);
fetch emp_sal_cursor into v_emp_record;
end loop;
close emp_sal_cursor;
end; 

可以使用for循环最优化:(注意:在for循环中它会自动的打开游标、提取游标,当提取完里面的数据后也会自动
的关闭游标

declare
cursor emp_sal_cursor is select employee_id,last_name,salary from employees where 
department_id = 80;
begin 
for c in emp_sal_cursor loop
dbms_output.put_line('employee_id:'||c.employee_id||', '||'last_name:'||c.last_name||', 
'||'salary:'||c.salary);
end loop;
end;


利用游标,调整公司中员工的工资:
工资范围            调整基数
0 - 5000              5%
5000 - 10000       3%
10000 - 15000     2%
15000 -               1%
实现:

declare 
  cursor emp_cursor is select employee_id,salary from employees;
  v_empid employees.employee_id%type;
  v_sal employees.salary%type;
  v_temp number(4,2);
begin 
  open emp_cursor;
  fetch emp_cursor into v_empid,v_sal;
  while emp_cursor%found loop
   if v_sal < 5000 then v_temp:=0.05;
   elsif v_sal < 10000 then v_temp:=0.03;
   elsif v_sal < 15000 then v_temp:=0.02;
   else v_temp:=0.01;
   end if;
  dbms_output.put_line(v_empid||','||v_sal);
  update employees
  set salary = salary * (1+v_temp)
  where employee_id = v_empid;
  fetch emp_cursor into v_empid,v_sal;
  end loop;
  close emp_cursor;
end;

用for循环实现

declare 
  cursor emp_cursor is select employee_id,salary from employees;
  v_temp number(4,2); 
begin 
  for c in emp_cursor loop
   if c.salary <5000 then v_temp:=0.05;
   elsif c.salary <10000 then v_temp:=0.03;
   elsif c.salary <15000 then v_temp:=0.02;
   else v_temp:=0.01;
  end if;
  update employees
  set salary = salary * (1+v_temp)
  where employee_id = c.employee_id;
  end loop;
end;

隐式游标:更新员工salary(涨工资10),如果该员工没有找到,则打印“查无此人”信息:

begin 
  update employees
  set salary = salary + 10
  where employee_id = 1001;
   if sql%notfound then dbms_output.put_line('查无此人');
   end if;
end;

异常:
预定义异常:(有24个预定义异常,可查表

declare
  v_sal employees.salary%type;
begin 
  select salary into v_sal from employees 
  where employee_id > 100;
  dbms_output.put_line(v_sal); 
exception
  when too_many_rows then dbms_output.put_line('输出的行数过多');
  when others then dbms_output.put_line('出现其它的异常了');
end;

非预定义异常:

declare
  e_deleteid_exception exception;
  pragma exception_init(e_deleteid_exception,-2292);
begin 
  delete from employees
  where employee_id = 100; 
exception
  when e_deleteid_exception then dbms_output.put_line('违反了完整性约束,故不能删除此用户');
  when others then dbms_output.put_line('出现其它的异常了');
end;

用户自定义异常:

declare
  e_sal_hight exception;
  v_sal employees.salary%type;
begin 
  select salary into v_sal from employees where employee_id = 100;
  if v_sal > 10000 then raise e_sal_hight;
  end if;
exception
  when e_sal_hight then dbms_output.put_line('工资太高了');
  when others then dbms_output.put_line('出现其它的异常了');
end;

通过select...into...查询某人的工资,若没找到则打印出“未找到此数据”:

declare
  v_sal employees.salary%type;
begin 
  select salary into v_sal from employees where employee_id = 1001;
exception
  when no_data_found then dbms_output.put_line('未找到此数据');
  when others then dbms_output.put_line('出现其它的异常了');
end;
更新指定员工工资,如工资小于300,则加100,对NO_DATA_FOUND异常,TOO_MANY_ROWS进行处理。
declare
  v_sal employees.salary%type;
begin 
  select salary into v_sal from employees where employee_id = 1001;
  if v_sal < 300 then update employees set salary = salary + 100 where employee_id =101;
  end if;
exception
  when no_data_found then dbms_output.put_line('未找到此数据');
  when too_many_rows then dbms_output.put_line('输出的行数太多了');
  when others then dbms_output.put_line('出现其它的异常了');
end;

自定义异常:
更新指定员工工资,增加100;若指定员工不在,则抛出异常:NO_RESULT;

declare 
  no_result exception;
begin 
  update employees set salary = salary + 100 where employee_id = 1001;
  if sql%notfound then raise no_result;
  end if;
exception 
  when no_result then dbms_output.put_line('查无此数据,更新失败'); 
  when others then dbms_output.put_line('出现其它异常'); 
end;


存储过程:
写个简单的hello_world存储函数

create or replace function hello_world 
return varchar2
is (相当于declare,可以在其后面定义变量、记录、游标)
begin 
  return 'helloworld';
end;
存储函数的调用:
begin 
  dbms_output.put_line(hello_world);
end;
或者:
select hello_world from dual;


带参数的存储函数:

create or replace function hello_world1(v_logo varchar2)
return varchar2
is 
begin 
  return 'helloworld'||v_logo;
end;
调用:
select hello_world1('shellway') from dual
或者:
begin 
  dbms_output.put_line(hello_world1('shellway'));
end;


定义一个获取系统时间的函数:

create or replace function get_sysdate
return varchar2
is 
begin 
  return to_char(sysdate,'yyyy-MM-dd HH24:mi:ss');
end;


定义带参数的函数,两个数相加

create or replace function add_param(v_num1 number,v_num2 number)
return number
is
  v_num3 number(10);
begin
  v_num3 := v_num1 + v_num2;
  return v_num3;
end;
调用:
select add_param(2,5) from dual;
或者:
begin 
  dbms_output.put_line(add_param(5,4));
end; 


定义一个函数:获取给定部门的工资总和,要求:部门号定义为参数,工资总额为返回值:

create or replace function get_sal(dept_id number)
return number
is 
  v_sumsal number(10) := 0;
  cursor salary_cursor is select salary from employees where department_id = dept_id;
begin 
  for c in salary_cursor loop 
  v_sumsal := v_sumsal + c.salary;
  end loop;
  return v_sumsal;
end;
调用:
select get_sal(80) from dual;


定义一个函数:获取给定部门的工资总和 和 该部门的员工总数(定义为OUT类型的参数)。
要求:部门号定义为参数,工资总额定义为返回值。

create or replace function get_sal(dept_id number,total_count out number)
return number
is 
 v_sumsal number(10) := 0;
 cursor salary_cursor is select salary from employees where department_id = dept_id;
begin 
  total_count := 0;
  for c in salary_cursor loop 
    v_sumsal := v_sumsal + c.salary;
    total_count := total_count + 1;
  end loop;
  return v_sumsal;
end;
调用:
declare
  v_count number(4);
begin 
  dbms_output.put_line(get_sal(80,v_count));
  dbms_output.put_line(v_count);
end;


定义一个存储过程:获取给定部门的工资总和(通过out参数),要求部门号和工资总额定义为参数。
(注意:存储过程和存储函数是不一样的,存储函数有返回值而存储过程没有,调用时候存储过程直接调用)

create or replace procedure get_sal1(dept_id number,sumsal out number)
is 
 cursor salary_cursor is select salary from employees where department_id = dept_id;
begin 
 sumsal := 0;
 for c in salary_cursor loop 
   sumsal := sumsal + c.salary;
 end loop;
 dbms_output.put_line(sumsal);
end;
调用:
declare 
  v_sal number(10):=0; 
begin 
 get_sal1(80,v_sal);
end;


对给定部门(作为输入参数)的员工进行加薪操作,若其到公司的时间在(?,95)期间,为其加薪5%

                                                                                          (95,98)                  3%

                                                                                          (98,?)                   1%
得到以下返回结果:为此次加薪公司每月额外付出多少成三(定义一个OUT型的输出参数)

create or replace procedure add_sal(dept_id number,temp out number)
is
  cursor sal_cursor is select employee_id,salary,hire_date 
  from employees where department_id = dept_id;
  v_temp number(4,2):=0;
begin 
  temp := 0;
  for c in sal_cursor loop
    if to_char(c.hire_date,'yyyy') < '1995' then v_temp:=0.05;
    elsif to_char(c.hire_date,'yyyy') < '1998' then v_temp:=0.03;
    else v_temp:=0.01;
    end if;

  update employees 
  set salary = salary * (1+v_temp) 
  where employee_id = c.employee_id;

  temp := temp + c.salary*v_temp; 
  end loop;
  dbms_output.put_line(temp);
end;
调用:
declare 
  v_i number(10):=0;
begin
  add_sal(80,v_i);
end;

触发器:
触发事件:在INSERT,UPDATE,DELETE情况下会触发TRIGGER
触发时间:该TRIGGER是在触发事件发生之前(BEFORE)还是之后(AFTER)
触发器本身:该TRIGGER被触发之后的目的和意图,正是触发器本身要做的事情,如PL/SQL块
触发频率:有语句级(STATEMENT)触发器和行级(ROW)触发器
写一个简单的触发器:

create or replace trigger update_emp_trigger
after
  update on employees
for each row (行级触发器,即每更新一条记录就会输出一次'helloworld',若没有这语句则是语句级触发器)
begin
  dbms_output.put_line('helloworld');
end;


使用:new,:old修饰符:

1、
create table emp1
as
select employee_id,salary,email from employees where department_id = 80;
2、
create or replace trigger update_emp_trigger2
after
  update on emp1
for each row
begin
  dbms_output.put_line('old salary:'||:old.salary||'new salary:'||:new.salary);
end;
3、
update emp1 set salary = salary + 100 ;


编写一个触发器,在对my_emp记录进行删除的时候,在my_emp_bak表中备份对应的记录

1、创建my_emp表:
create table my_emp 
as
select employee_id,salary from employees ;
2、创建my_emp_bak表:
create table my_emp_bak
as
select employee_id,salary from employees where 1=2;
3、检查创建的表中的记录:
select * from my_emp
select * from my_emp_bak
4、创建一个触发器:
create or replace trigger delete_emp_trigger 
before
  delete on my_emp 
for each row
begin
  insert into my_emp_bak 
  values(:old.employee_id,:old.salary);
end;
5、执行含有触发器时间的语句:
delete from my_emp
6、检查触发器执行后的结果:
select * from my_emp
select * from my_emp_bak

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