项目生命周期:
瀑布模型
拿到一个项目后,首先:分析需要用到的SQL语句;
其次:分析需要定义的变量初始值是多少,怎么得到最终值;
案例一:
统计每年入职的员工数量以及总数量:
SQL语句:select to_char(hiredate,‘yyyy‘) from emp;--to_char(hiredate,‘yyyy‘) :hiredate原本的格式是yyyy-mm-dd但是我们只需要年份,则强制转换为char型,并且格式为yyyy,强制转换语法:to_ 目的类型(目标字段,格式)
需要遍历整个表,那么需要用到光标->循环->退出条件:%notfound
变量:phiredate varchar2(20)
计数器:
count80 number := 0;
count82 number := 0;
count87 number := 0;
count89 number := 0;
set serveroutput on;
declare
cursor c is select to_char(hiredate,‘yyyy‘) from emp;--定义光标
phiredate varchar2(20);
count80 number := 0;
count82 number := 0;
count87 number := 0;
count89 number := 0;
begin
open c;--打开光标
loop
fetch c into phiredate ;--取出员工的入职年份
exit when c%notfound;--关闭循环的条件
if phiredate= ‘1980‘ then count80 number := count80+ 1;
elsif phiredate= ‘1982‘ then count82 number := count82+ 1;
elsif phiredate= ‘1987‘ then count87 number := count87+ 1;
else count87 number := count87+ 1;
end if;
end loop;
close c;
dbms_output.put_line(‘tatal:‘||count80+count82+count87+count89)
end;
/
案例二
SQL语句:select no,sal from emp;
需要遍历整个表,那么需要用到光标->循环->退出条件:%notfound
变量:pno emp.no%type;
psal emp.sal%type;
涨工资人数:countemp number := 0;
涨后的工资总额:saltotal number;
select sum(sal) into saltotal from emp;
涨后的工资总额 = 涨前的工资总额 + sal*0.1;
set serveroutput on
declare
cursor c is select empno,sal from order by sal;
pno emp.no%type;
psal emp.sal%type;
countemp number := 0;--涨工资的人数
saltatol number;--涨后的工作总额
begin
select sum(sal) into saltatol from emp;--涨工资前的初始值
open c;
loop
exit when saltotal >50000;
fetch c into pno,psal;
exit when c%notfound;
update emp set sal := sal*1.1 where no = pno;--涨工资
countemp := countemp + 1;--人数+1
end loop;
close c;
commit;
dbms_output.out_put(‘人数= ‘||countepm||‘,涨后的工资总额:‘||saltatol);
end:
/
案例三
实现部门分段(6000分以上,6000》且3000《,3000以下)统计各工资段的职工人数,以及各部门的工资总额(不包括奖金)
首先需要创建存储结果的表msg:create table msg(deptno number;count1 number;count2 number; count3 number;saltotal number);
set serveroutput on
declare
cursor cdept is select deptno from dept;--部门的光标
pdeptno dept.deptno %type;--部门光标对应的变量
cursor cemp(deptno) is select sal from emp where no = deptno;--部门工资的光标
psal emp.sal %type;--部门工资光标对应的变量
count1 number;count2 number;count3 number;--每个阶段员工计数器
begin
open cdept;
loop
fetch cdept into pdeptno;--取出一个部门
exit when cdepy%notfound;
count1 :=0;count2 :=0;count3 :=0;--初始化计数器
select sum(sal) into saltatol from emp where deptno = pdeptno;--计算部门工资总额
open cemp(pdeptno)
loop
fetch cemp into psal;--取出每一个员工的薪资
exit when cemp%noufound;
if psal <3000 then count1 := count1 +1;--判断工资范围
elsif psal>6000 then count3 := count3 +1;
else count2 := count2 +1;
end if;
end loop;
close cemp;
insert into msg value(pdeptno,count1,count2,count3,saltatol);--保存当前部门的结果
end loop;
close cdept;
end:
/
案例四
按照系分段统计(成绩小于60,大于85,中间段)课程为‘大学物理’各个分数段的学生人数,以及各系学生的平均成绩;
、
set serveroutput on
declare
cersor cdept is select dno ,dname from dep;
pdno dep.dno%type;
cursor cgrade(coursename varchar2,depno number) is select grade from sc where cno = (select cno from course where cname = courname) and sno in (select sno from student where dno = depno)--成绩光标
pgrade sc.grade % type;
count1 number;count2 number;count3 number;--每个分数段人数计数器
avggrade number;--平均成绩
pcoursename varchar2 :=‘大学物理‘;
begin
open cdept;
loop
fetch cdept into pdno,pdname;
exit when cdept%notfound;
count1 :=0;count2 :=0;count3 :=0;--初始化计数器
select avg(grade) into avggrade from sc where cno = (select cno from course where cname = courname) and sno in (select sno from student where dno = depno)
open cgrade (pcoursename,pdno);
loop
fetch cgrade into pgrade;
exit when cgrade %notfound;
if psal <60 then count1 := count1 +1;--判断工资范围
elsif psal>85 then count3 := count3 +1;
else count2 := count2 +1;
end if;
end loop;
end loop;
close cgrade;
insert into msg value (pcoursename,count1,count2,count3,avggrade);
end loop;
close cdept;
commit;
dbms_output.put_line(‘统计完成‘);
end:/