PL/SQL基础
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平时基本都要写些小的PL/SQL程序,触发器,函数,包等,下面做了些小例子,麻雀随小,五脏俱全。可以举一反三。
conn hr/hr
SQL>create table emp as select * from employees;
SQL>create table dept as select * from departments
PL/SQL 块
Declare
v_ename varchar2(20);
Begin
select first_name into v_ename from employees where employee_id=&no;
dbms_output.put_line('The name of employee is :' || v_ename);
Exception
WHEN NO_DATA_FOUND THEN
dbms_output.put_line('please input the right employee number');
End;
/
Stored Procedure:
create or replace procedure update_sal(name varchar2,newsal number)
IS
BEGIN
update emp set salary=newsal where lower(first_name)=lower(name);
commit;
end;
函数:
create or replace function annual_income(name varchar2)
RETURN NUMBER IS
annual_salary number(7,2);
BEGIN
select salary*(12+nvl(COMMISSION_PCT,0)) into annual_salary from emp where lower(first_name)=lower(name);
return annual_salary;
END;
/
函数的执行
var income number
call annual_income('Donald') into :income;
print income
包:
主函数
Create or replace PACKAGE emp_pkg IS
procedure update_sal(name varchar2, newsal number);
Function annual_income(name varchar2) return number;
end;
/
函数体:
create or replace PACKAGE BODY emp_pkg IS
procedure update_sal(name varchar2,newsal number) IS
BEGIN
update emp set salary=newsal where lower(first_name)=lower(name);
commit;
end;
function annual_income(name varchar2) RETURN NUMBER IS
annual_salary number(7,2);
BEGIN
select salary*(12+nvl(COMMISSION_PCT,0)) into annual_salary from emp where lower(first_name)=lower(name);
return annual_salary;
end;
end;
/
调用例子:
SQL>call emp_pkg.update_sal('Donald','2700');
SQL>var income number
SQL>call emp_pkg.annual_income('Donald') into :income;
SQL>print income
触发器
create or replace trigger update_cascade
After update of department_id on dept
for each row
begin
update emp set department_id=:new.department_id where department_id=:old.department_id;
end;
/
使用标量变量
SQL> set serveroutput on
Declare
v_ename varchar2(20);
v_sal number(8,2);
c_tax_rate CONSTANT number(3,2):=0.03;
v_tax_sal number(8,2);
Begin
select first_name,salary into v_ename,v_sal from emp where employee_id=&eno;
v_tax_sal:=v_sal*c_tax_rate;
dbms_output.put_line('Employee name:'||v_ename);
dbms_output.put_line('Employee salary:'||v_sal);
dbms_output.put_line('Employee tax:'||v_tax_sal);
END;
/
上面的写法的缺点是万一数据库的表的字段长度发生了变化,则需要去修改上面的程序代码。
所以程序的维护性很差。
所以建议用%TYPE,它会按照数据库的列或其他的变量来确定新变量的类型和长度。下面是一个例子:
Declare
v_ename emp.first_name%TYPE;
v_sal EMP.SALARY%TYPE;
c_tax_rate CONSTANT number(3,2):=0.03;
v_tax_sal v_sal%TYPE;
Begin
select first_name,salary into v_ename,v_sal from emp where employee_id=&eno;
v_tax_sal:=v_sal*c_tax_rate;
dbms_output.put_line('Employee name:'||v_ename);
dbms_output.put_line('Employee salary:'||v_sal);
dbms_output.put_line('Employee tax:'||v_tax_sal);
END;
/
使用复合变量:指用于存放多个变量的变量。
它包括:PL/SQL记录,PL/SQL表,嵌套表以及VARRAY四种复合类型。
1,PL/SQL记录
Declare
TYPE emp_record_type IS RECORD(
name emp.first_name%TYPE,
salary emp.salary%TYPE,
title emp.job_id%TYPE);
emp_record emp_record_type;
BEGIN
select first_name,salary,job_id into emp_record from emp where employee_id=190;
dbms_output.put_line('first_name:' || emp_record.name);
END;
/
2,PL/SQL表
Declare
TYPE ename_table_type IS TABLE OF emp.first_name%TYPE
INDEX BY BINARY_INTEGER;
ename_table ename_table_type;
BEGIN
Select first_name into ename_table(-1) from emp where employee_id=190;
dbms_output.put_line('Frist_name:'|| ename_table(-1));
END;
/
ename_table(-1) 则表示下表为-1的元素。
3,嵌套表
4,VARRY
参照变量:指用于存放数值的指针的变量。在编写PL/SQL程序时,可以使用游标变量(REF CURSOR)和对象类型变量REF OBJ_TYPE等两种参照变量类型。
1,REF CURSOR
Declare
TYPE C1 IS REF CURSOR;
EMP_CURSOR C1;
V_ENAME EMP.FIRST_NAME%TYPE;
V_SAL EMP.SALARY%TYPE;
BEGIN
OPEN EMP_CURSOR FOR
SELECT first_name ,salary from emp where department_id=30;
LOOP
FETCH EMP_CURSOR INTO V_ENAME,V_SAL;
EXIT WHEN EMP_CURSOR%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(V_ENAME);
END LOOP;
CLOSE EMP_CURSOR;
END;
/
2,REF OBJ_TYPE
非PL/SQL变量:当在PL/SQL中引用非PL/SQL变量时,必须要在非PL/SQL变量前加冒号(:)
例如:
var name varchar2(10)
begin
select first_name into :name from emp where employee_id=190;
end;
/
SQL> print name
NAME
--------------------------------
Timothy
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