七、函数-存储过程-触发器

一、函数

函数分为(1)系统函数,(2)自定义函数。

其中自定义函数又可以分为(1)标量值函数(返回单个值),(2)表值函数(返回查询结果)

本文主要介绍自定义函数的使用。

(1)编写一个函数求该银行的金额总和

create function GetSumCardMoney()
returns money 
as
begin
	declare @AllMOney money
	select @AllMOney = (select SUM(CardMoney) from BankCard)
	return @AllMOney
end

函数调用

select dbo.GetSumCardMoney()

上述函数没有参数,下面介绍有参数的函数的定义及使用

(2)传入账户编号,返回账户真实姓名

create function GetNameById(@AccountId int)
returns  varchar(20)
as
begin
	declare @RealName varchar(20)
	select @RealName = (select RealName from AccountInfo where AccountId = @AccountId)
	return @RealName
end

函数调用

print dbo.GetNameById(2)

(3)传递开始时间和结束时间,返回交易记录(存钱取钱),交易记录中包含 真实姓名,卡号,存钱金额,取钱金额,交易时间。

方案一(逻辑复杂,函数内容除了返回结果的sql语句还有其他内容,例如定义变量等):

create function GetExchangeByTime(@StartTime varchar(30),@EndTime varchar(30))
returns @ExchangeTable table
(
	RealName varchar(30),  --真实姓名
	CardNo varchar(30),    --卡号
	MoneyInBank money,     --存钱金额
	MoneyOutBank money,    --取钱金额
	ExchangeTime smalldatetime  --交易时间
)
as
begin
	insert into @ExchangeTable
	select AccountInfo.RealName,CardExchange.CardNo,CardExchange.MoneyInBank,
	CardExchange.MoneyOutBank,CardExchange.ExchangeTime from CardExchange
	left join BankCard on CardExchange.CardNo = BankCard.CardNo
	left join AccountInfo on BankCard.AccountId = AccountInfo.AccountId
	where CardExchange.ExchangeTime between @StartTime+' 00:00:00' and @EndTime+' 23:59:59'
	return
end

函数调用

select * from GetExchangeByTime('2018-6-1','2018-7-1')

方案二(逻辑简单,函数内容直接是一条sql查询语句):

create function GetExchangeByTime(@StartTime varchar(30),@EndTime varchar(30))
returns table
as
	return
	select AccountInfo.RealName,CardExchange.CardNo,CardExchange.MoneyInBank,
	CardExchange.MoneyOutBank,CardExchange.ExchangeTime from CardExchange
	left join BankCard on CardExchange.CardNo = BankCard.CardNo
	left join AccountInfo on BankCard.AccountId = AccountInfo.AccountId
	where CardExchange.ExchangeTime between @StartTime+' 00:00:00' and @EndTime+' 23:59:59'
go

函数调用:

select * from GetExchangeByTime('2018-6-19','2018-6-19')

(4)查询银行卡信息,将银行卡状态1,2,3,4分别转换为汉字“正常,挂失,冻结,注销”,根据银行卡余额显示银行卡等级 30万以下为“普通用户”,30万及以上为”VIP用户”,分别显示卡号,身份证,姓名,余额,用户等级,银行卡状态。

方案一:直接在sql语句中使用case when

select * from AccountInfo
select * from BankCard
select CardNo 卡号,AccountCode 身份证,RealName 姓名,CardMoney 余额,
case
	when CardMoney < 300000 then '普通用户'
	else 'VIP用户' 
end 用户等级,
case
	when CardState = 1 then '正常'
	when CardState = 2 then '挂失'
	when CardState = 3 then '冻结'
	when CardState = 4 then '注销'
	else '异常'
end 卡状态
from BankCard inner join AccountInfo on BankCard.AccountId = AccountInfo.AccountId

方案二:将等级和状态用函数实现

create function GetGradeByMoney(@myMoney int)
returns varchar(10)
as
begin
	declare @result varchar(10)
	if @myMoney < 3000 
		set @result = '普通用户'
	else
		set @result = 'VIP用户'
	return @result
end
go

create function GetStatusByNumber(@myNum int)
returns varchar(10)
as
begin
	declare @result varchar(10)
	if @myNum = 1
		set @result = '正常'
	else if @myNum = 2
		set @result = '挂失'
	else if @myNum = 3
		set @result = '冻结'
	else if @myNum = 4
		set @result = '注销'
	else
		set @result = '异常'	
	return @result
end
go

函数调用实现查询功能

select CardNo 卡号,AccountCode 身份证,RealName 姓名,CardMoney 余额,
dbo.GetGradeByMoney(CardMoney) 账户等级,dbo.GetStatusByNumber(CardState) 卡状态
from BankCard inner join AccountInfo on BankCard.AccountId = AccountInfo.AccountId

(5)编写函数,根据出生日期求年龄,年龄求实岁,例如:

​ 生日为2000-5-5,当前为2018-5-4,年龄为17岁
​ 生日为2000-5-5,当前为2018-5-6,年龄为18岁

测试数据如下:

create table Emp
(
	EmpId int primary key identity(1,2), --自动编号
	empName varchar(20), --姓名
	empSex varchar(4),   --性别
	empBirth smalldatetime --生日
)
insert into Emp(empName,empSex,empBirth) values('刘备','男','2008-5-8')
insert into Emp(empName,empSex,empBirth) values('关羽','男','1998-10-10')
insert into Emp(empName,empSex,empBirth) values('张飞','男','1999-7-5')
insert into Emp(empName,empSex,empBirth) values('赵云','男','2003-12-12')
insert into Emp(empName,empSex,empBirth) values('马超','男','2003-1-5')
insert into Emp(empName,empSex,empBirth) values('黄忠','男','1988-8-4')
insert into Emp(empName,empSex,empBirth) values('魏延','男','1998-5-2')
insert into Emp(empName,empSex,empBirth) values('简雍','男','1992-2-20')
insert into Emp(empName,empSex,empBirth) values('诸葛亮','男','1993-3-1')
insert into Emp(empName,empSex,empBirth) values('徐庶','男','1994-8-5')

函数定义:

create function GetAgeByBirth(@birth smalldatetime)
returns int
as
begin
	declare @age int
	set @age = year(getdate()) - year(@birth)
	if month(getdate()) < month(@birth)
		set @age = @age - 1
	if month(getdate()) = month(@birth) and day(getdate()) < day(@birth)
		set @age = @age -1
	return @age
end

函数调用实现查询

select *,dbo.GetAgeByBirth(empBirth) 年龄 from Emp

二、触发器

触发器分类:(1) “Instead of”触发器(2)“After”触发器
“Instead of”触发器:在执行操作之前被执行
“After”触发器:在执行操作之后被执行

触发器中后面的案例中需要用到的表及测试数据如下:

--部门
create table Department
(
	DepartmentId varchar(10) primary key , --主键,自动增长
	DepartmentName nvarchar(50), --部门名称
)
--人员信息
create table People
(
	PeopleId int primary key identity(1,1), --主键,自动增长
	DepartmentId varchar(10), --部门编号,外键,与部门表关联
	PeopleName nvarchar(20), --人员姓名
	PeopleSex nvarchar(2), --人员性别
	PeoplePhone nvarchar(20), --电话,联系方式
)
insert into Department(DepartmentId,DepartmentName)
values('001','总经办')
insert into Department(DepartmentId,DepartmentName)
values('002','市场部')
insert into Department(DepartmentId,DepartmentName)
values('003','人事部')
insert into Department(DepartmentId,DepartmentName)
values('004','财务部')
insert into Department(DepartmentId,DepartmentName)
values('005','软件部')
insert into People(DepartmentId,PeopleName,PeopleSex,PeoplePhone)
values('001','刘备','男','13558785478')
insert into People(DepartmentId,PeopleName,PeopleSex,PeoplePhone)
values('001','关羽','男','13558788785')
insert into People(DepartmentId,PeopleName,PeopleSex,PeoplePhone)
values('002','张飞','男','13698547125')

(1)假设有部门表和员工表,在添加员工的时候,该员工的部门编号如果在部门表中找不到,则自动添加部门信息,部门名称为”新部门”。

编写触发器:

create trigger tri_InsertPeople on People
after insert
as
if not exists(select * from Department where DepartmentId = (select DepartmentId from inserted))
	insert into Department(DepartmentId,DepartmentName)
	values((select DepartmentId from inserted),'新部门')
go

测试触发器:

insert People(DepartmentId,PeopleName,PeopleSex,PeoplePhone)
values('009','赵云','男','13854587456')

我们会发现,当插入赵云这个员工的时候会自动向部门表中添加数据。

(2)触发器实现,删除一个部门的时候将部门下所有员工全部删除。

编写触发器:

create trigger tri_DeleteDept on Department
after delete
as
delete from People where People.DepartmentId = 
(select DepartmentId from deleted)
go

测试触发器:

delete Department where DepartmentId = '001'

我们会发现当我们删除此部门的时候,同时会删除该部门下的所有员工

(3)创建一个触发器,删除一个部门的时候判断该部门下是否有员工,有则不删除,没有则删除。

编写触发器:

drop trigger tri_DeleteDept	--删除掉之前的触发器,因为当前触发器也叫这个名字
create trigger tri_DeleteDept on Department
Instead of delete
as
  if not exists(select * from People where DepartmentId = (select DepartmentId from deleted))
  begin
	delete from Department where DepartmentId = (select DepartmentId from deleted)
  end
go

测试触发器:

delete Department where DepartmentId = '001'
delete Department where DepartmentId = '002'
delete Department where DepartmentId = '003'

我们会发现,当部门下没有员工的部门信息可以成功删除,而部门下有员工的部门并没有被删除。

(4)修改一个部门编号之后,将该部门下所有员工的部门编号同步进行修改

编写触发器:

create trigger tri_UpdateDept on Department
after update
as
	update People set DepartmentId = (select DepartmentId from inserted)
	where DepartmentId = (select DepartmentId from deleted)
go

测试触发器:

update Department set DepartmentId = 'zjb001' where DepartmentId='001'

我们会发现不但部门信息表中的部门编号进行了修改,员工信息表中部门编号为001的信息也被一起修改了。

三、存储过程

存储过程(Procedure)是SQL语句和流程控制语句的预编译集合。

(1)没有输入参数,没有输出参数的存储过程。

定义存储过程实现查询出账户余额最低的银行卡账户信息,显示银行卡号,姓名,账户余额

--方案一
create proc proc_MinMoneyCard
as
    select top 1 CardNo 银行卡号,RealName 姓名,CardMoney 余额
    from BankCard inner join AccountInfo on BankCard.AccountId = AccountInfo.AccountId
    order by CardMoney asc
go

--方案二:(余额最低,有多个人则显示结果是多个)
create proc proc_MinMoneyCard
as
    select CardNo 银行卡号,RealName 姓名,CardMoney 余额
    from BankCard inner join AccountInfo on BankCard.AccountId = AccountInfo.AccountId
    where CardMoney=(select MIN(CardMoney) from BankCard)
go

执行存储过程:

exec proc_MinMoneyCard

(2)有输入参数,没有输出参数的存储过程

模拟银行卡存钱操作,传入银行卡号,存钱金额,实现存钱操作

create proc proc_CunQian
@CardNo varchar(30),
@MoneyInBank money
as
    update BankCard set CardMoney = CardMoney + @MoneyInBank where CardNo = @CardNo
    insert into CardExchange(CardNo,MoneyInBank,MoneyOutBank,ExchangeTime)
    values(@CardNo,@MoneyInBank,0,GETDATE())
--go

执行存储过程:

exec proc_CunQian '6225125478544587',3000

(3)有输入参数,没有输出参数,但是有返回值的存储过程(返回值必须整数)。

模拟银行卡取钱操作,传入银行卡号,取钱金额,实现取钱操作,取钱成功,返回1,取钱失败返回-1

create proc proc_QuQian
@CardNo varchar(30),
@MoneyOutBank money
as
    update BankCard set CardMoney = CardMoney - @MoneyOutBank where CardNo = @CardNo
    if @@ERROR <> 0
        return -1
    insert into CardExchange(CardNo,MoneyInBank,MoneyOutBank,ExchangeTime)
    values(@CardNo,0,@MoneyOutBank,GETDATE())
    return 1
go

执行存储过程:

declare @returnValue int
exec @returnValue = proc_QuQian '662018092100000002',1000000
print @returnValue

(4)有输入参数,有输出参数的存储过程

查询出某时间段的银行存取款信息以及存款总金额,取款总金额,传入开始时间,结束时间,显示存取款交易信息的同时,返回存款总金额,取款总金额。

create proc proc_SelectExchange
    @startTime varchar(20),  --开始时间
    @endTime varchar(20),    --结束时间
    @SumIn money output,     --存款总金额
    @SumOut money output    --取款总金额
as
select @SumIn = (select SUM(MoneyInBank) from CardExchange 
				where ExchangeTime between @startTime+' 00:00:00' and @endTime+' 23:59:59')
select @SumOut = (select SUM(MoneyOutBank) from CardExchange 
				where ExchangeTime between @startTime+' 00:00:00' and @endTime+' 23:59:59')
select * from CardExchange 
where ExchangeTime between @startTime+' 00:00:00' and @endTime+' 23:59:59'
go

执行存储过程:

declare @SumIn money     --存款总金额
declare @SumOut money   --取款总金额
exec proc_SelectExchange '2018-1-1','2018-12-31',@SumIn output,@SumOut output
select @SumIn
select @SumOut

(5)具有同时输入输出参数的存储过程

密码升级,传入用户名和密码,如果用户名密码正确,并且密码长度<8,自动升级成8位密码

--有输入输出参数(密码作为输入参数也作为输出参数)
--密码升级,传入用户名和密码,如果用户名密码正确,并且密码长度<8,自动升级成8位密码
select FLOOR(RAND()*10) --0-9之间随机数
create proc procPwdUpgrade
@cardno nvarchar(20),
@pwd nvarchar(20) output
as
	if not exists(select * from BankCard where CardNo=@cardno and CardPwd=@pwd)
		set @pwd = ''
	else
	begin
		if len(@pwd) < 8
		begin
			declare @len int = 8- len(@pwd)
			declare @i int = 1
			while @i <= @len
			begin
				
				set @pwd = @pwd + cast(FLOOR(RAND()*10) as varchar(1))
				set @i = @i+1
			end
			update BankCard set CardPwd = @pwd where CardNo=@cardno
		end
	end
go
declare @pwd nvarchar(20) = '123456'
exec procPwdUpgrade '6225547854125656',@pwd output
select @pwd

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