有些初学者在调用存储过程时容易出现一些错误，下面我就不同的返回参数而言举个用户登录常用的例子做一些简单的讨论：(由简单--->>深入)
创建数据库：(Student)
创建用户表：(Users)
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use Student
go
create table Users
(
id int identity(1, 1) primary key,
name nvarchar(20) not null,
password nvarchar(20) not null
)
use Student
go
create table Users
(
id int identity(1, 1) primary key,
name nvarchar(20) not null,
password nvarchar(20) not null
)
1.带输入参数的存储过程
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create procedure proc_login
@name nvarchar(20),
@password nvarchar(20)
as
begin
select *
from Users
where name = @name and password = @password
end
go
create procedure proc_login
@name nvarchar(20),
@password nvarchar(20)
as
begin
select *
from Users
where name = @name and password = @password
end
go
调用带输入参数的存储过程
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//连接数据库的字符串
private string connectionString = ConfigurationManager.AppSetting["connectionString"];
//数据层的登录方法
public static User Login(string name, string password)
{
User user = null;
using (SqlConnection conn = new SqlConnection(connectionString))
{
SqlCommand cmd = new SqlCommand("proc_login", conn);
cmd.CommandType = CommandType.StoredProcedure; //指定调用存储过程
//指定参数
cmd.Parameters.Add("@name", SqlDbType.nvarchar, 20).Value = name;
cmd.Parameters.Add("@password", SqlDbType.nvarchar, 20).Value = password;
conn.open();
using(SqlDataReader sdr = cmd.ExecuteReader())
{
if(sdr.Read())
{
user = new User((int)sdr["id"], sdr["name"].ToString(), sdr["password"].ToString());
}
}
conn.Close();
}
return user;
}
//连接数据库的字符串
private string connectionString = ConfigurationManager.AppSetting["connectionString"];
//数据层的登录方法
public static User Login(string name, string password)
{
User user = null;
using (SqlConnection conn = new SqlConnection(connectionString))
{
SqlCommand cmd = new SqlCommand("proc_login", conn);
cmd.CommandType = CommandType.StoredProcedure; //指定调用存储过程
//指定参数
cmd.Parameters.Add("@name", SqlDbType.nvarchar, 20).Value = name;
cmd.Parameters.Add("@password", SqlDbType.nvarchar, 20).Value = password;
conn.open();
using(SqlDataReader sdr = cmd.ExecuteReader())
{
if(sdr.Read())
{
user = new User((int)sdr["id"], sdr["name"].ToString(), sdr["password"].ToString());
}
}
conn.Close();
}
return user;
}
2.带输入输出参数的存储过程
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create procedure proc_login
@name nvarchar(20),
@password nvarchar(20),
@message nvarchar(50) output //用于输出用户登录的信息
as
begin
//判断用户名是否存在
if exists (select * from Users where name = @name)
begin
//判断密码是否正确
select * from Users where name = @name and password = @password
//返回的行数〉0
if @@rowcount > 0
begin
set @message = '登录成功！'
end
else
begin
set @message = '密码错误！'
end
end
else
begin
set @message = '用户名不存在！'
end
//在过程中如果有错误
if @@error <> 0
begin
set @message = '登录失败！'
end
end
go
create procedure proc_login
@name nvarchar(20),
@password nvarchar(20),
@message nvarchar(50) output //用于输出用户登录的信息
as
begin
//判断用户名是否存在
if exists (select * from Users where name = @name)
begin
//判断密码是否正确
select * from Users where name = @name and password = @password
//返回的行数〉0
if @@rowcount > 0
begin
set @message = '登录成功！'
end
else
begin
set @message = '密码错误！'
end
end
else
begin
set @message = '用户名不存在！'
end
//在过程中如果有错误
if @@error <> 0
begin
set @message = '登录失败！'
end
end
go
调用带输入输出参数的存储过程
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//数据层的登录方法
public static User Login(string name, string password, out string message)
{
User user = null;
using (SqlConnection conn = new SqlConnection(connectionString))
{
SqlCommand cmd = new SqlCommand("proc_login", conn);
cmd.CommandType = CommandType.StoredProcedure; //指定调用存储过程
//指定参数
cmd.Parameters.Add("@name", SqlDbType.nvarchar, 20).Value = name;
cmd.Parameters.Add("@password", SqlDbType.nvarchar, 20).Value = password;
SqlParameter mes = new SqlParameter("@message", SqlDbType.nvarchar, 50);
mes.Direction = ParameterDiraction.Output;
cmd.Add(mes);
conn.open();
using(SqlDataReader sdr = cmd.ExecuteReader())
{
message = mes.Value.ToString();
if(sdr.Read())
{
user = new User((int)sdr["id"], sdr["name"].ToString(), sdr["password"].ToString());
}
}
conn.Close();
}
return user;
}
//数据层的登录方法
public static User Login(string name, string password, out string message)
{
User user = null;
using (SqlConnection conn = new SqlConnection(connectionString))
{
SqlCommand cmd = new SqlCommand("proc_login", conn);
cmd.CommandType = CommandType.StoredProcedure; //指定调用存储过程
//指定参数
cmd.Parameters.Add("@name", SqlDbType.nvarchar, 20).Value = name;
cmd.Parameters.Add("@password", SqlDbType.nvarchar, 20).Value = password;
SqlParameter mes = new SqlParameter("@message", SqlDbType.nvarchar, 50);
mes.Direction = ParameterDiraction.Output;
cmd.Add(mes);
conn.open();
using(SqlDataReader sdr = cmd.ExecuteReader())
{
message = mes.Value.ToString();
if(sdr.Read())
{
user = new User((int)sdr["id"], sdr["name"].ToString(), sdr["password"].ToString());
}
}
conn.Close();
}
return user;
}
3.带返回值得存储过程
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create procedure proc_login
@name nvarchar(20),
@password nvarchar(20)
as
declare @message nvarchar(50) output //用于返回用户登录的信息
begin
//判断用户名是否存在
if exists (select * from Users where name = @name)
begin
//判断密码是否正确
select * from Users where name = @name and password = @password
//返回的行数〉0
if @@rowcount > 0
begin
set @message = '登录成功！'
end
else
begin
set @message = '密码错误！'
end
end
else
begin
set @message = '用户名不存在！'
end
//在过程中如果有错误
if @@error <> 0
begin
set @message = '登录失败！'
end
return @message
end
go
create procedure proc_login
@name nvarchar(20),
@password nvarchar(20)
as
declare @message nvarchar(50) output //用于返回用户登录的信息
begin
//判断用户名是否存在
if exists (select * from Users where name = @name)
begin
//判断密码是否正确
select * from Users where name = @name and password = @password
//返回的行数〉0
if @@rowcount > 0
begin
set @message = '登录成功！'
end
else
begin
set @message = '密码错误！'
end
end
else
begin
set @message = '用户名不存在！'
end
//在过程中如果有错误
if @@error <> 0
begin
set @message = '登录失败！'
end
return @message
end
go
调用带返回值得存储过程
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//数据层的登录方法
public static User Login(string name, string password, out string message)
{
User user = null;
using (SqlConnection conn = new SqlConnection(connectionString))
{
SqlCommand cmd = new SqlCommand("proc_login", conn);
cmd.CommandType = CommandType.StoredProcedure; //指定调用存储过程
//指定参数
cmd.Parameters.Add("@name", SqlDbType.nvarchar, 20).Value = name;
cmd.Parameters.Add("@password", SqlDbType.nvarchar, 20).Value = password;
SqlParameter mes = new SqlParameter("@message", SqlDbType.nvarchar, 50);
mes.Direction = ParameterDiraction.ReturnValue; //注意这里指定返回值
cmd.Add(mes);
conn.open();
using(SqlDataReader sdr = cmd.ExecuteReader())
{
message = mes.Value.ToString();
if(sdr.Read())
{
user = new User((int)sdr["id"], sdr["name"].ToString(), sdr["password"].ToString());
}
}
conn.Close();
}
return user;
}