I want to run this query in C#
SELECT *
FROM [FirstDataBase].[dbo].[table1]
INNER JOIN [SecondDataBase].[dbo].[table2]
and my code is :
SqlConnection cn = new SqlConnection(myConnectionString);
SqlCommand cmd = new SqlCommand(#"SELECT * FROM [FirstDataBase].[dbo].[table1]
INNER JOIN [SecondDataBase].[dbo].[table2]");
cmd.Connection = cn; // here is my question !!!
cn.Open();
int x = (int)cmd.ExecuteScalar();
but my query needs two connection string ... one for [FirstDataBase] and second
for [SecondDataBase]...
How can I do this ?
How can I insert two SqlConnection or ConnectionString to one SqlCommand ? or
How can I do it in other ways ?
I've actually reread your question, you don't need two connection strings. Your query command can affect any database you wish, once you've connected. For instance:
string query = #"SELECT * FROM [FirstDataBase].[dbo].[table1]
INNER JOIN [SecondDataBase].[dbo].[table2]";
using(SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionString[#"db"].ConnectionString))
using(SqlCommand command = new SqlCommand(query, connection))
{
// Logic
}
That would impact both databases should your query impact both of them. Your able to use the same hierarchy that is present in SQL Management Studio to perform your task.
You only need to connect to the first database. The query will then connect from there to the second database. Alternatively you can connect to just the second database if you prefer but the key point is that you only require one connection.
The same principle applies if you are using Management Studio, you would connect to the first database and then run the query joining across to the second.
Obviously this assumes that the first database can communicate with the second (as #Tim Medora pointed out in the comments).
If the databases are on different servers you can create a "Linked Server" in Management Studio.
From within your main database goto Server Objects -> Linked Servers.
Right-click on Linked Servers then hit "New Linked Server"
On the General page select the Type of Server you'd like to link to and enter credentials if needed.
Add the local user that will have access to the linked database and enter the "remote" user that you want to be and press Ok.
Done.
Then in front of the database name you need to specify which server. An example:
select * from [2.2.2.2].[Test].[dbo].[MyTable]
join [1.1.1.1].[OtherDb].[dbo].[OtherTable] on ...etc
The great part about Linked Servers is that you map the user so that the same user doesn't have to exist on both machines. The database with the link then automatically logs you in the the other one.
Your query is database specified "[FirstDataBase].[dbo].[table1]". So you just to connect to a database (even can be a database other that [FirstDataBase] or [SecondDataBase]). Your code should works well.
Related
I am developing a web site, it uses SQL Server 2008 R2 Express for its database. And in testing, there is a lot of data and images stored into this database.
According to wiki, the SQL Server Express edition has a 10 GB size limit. When I insert data and reach the limit, what exception will be thrown? Or, how do I detect the approaching limit problem by codes ?
I use EF 5 with code-first approach to insert large data set.
In tests I have seen that:
sp_spaceused
won't work as expected, it showed 12GB after deleting lots of records. And the other answers regarding query sys.databases were not clear enough to me.
Searching around I found a very good explanation regarding SQL Server 2012 Express Edition 10GB Size Limit on Ramons weblog [EDIT2018 updated link]
SELECT
[name] AS [Filename],
[size]/128.0 AS [Filesize],
CAST(FILEPROPERTY([name],'SpaceUsed') AS int)/128.0 AS [UsedSpaceInMB],
[size]/128.0 - CAST(FILEPROPERTY([name],'SpaceUsed') AS int)/128.0 AS [AvailableSpaceInMB],
[physical_name] AS [Path]
FROM sys.database_files
"... space includes the transaction log and it also includes all unused space within these files. .... SQL Server Express will start complaining when it cannot reserve any more space for the datafile."
So checking
CAST(FILEPROPERTY([name],'SpaceUsed') AS int)/128.0 AS [UsedSpaceInMB]
seems to be the best option.
In combination with EF in c# my request to the DB looks like
string sqlSelect = "SELECT CAST(FILEPROPERTY([name],'SpaceUsed') AS int)/128.0 AS [UsedSpaceInMB] FROM sys.database_files";
var dbResult = dbInstance.Database.SqlQuery<Decimal>(sqlSelect).FirstOrDefault();
double spaceUsedInGb = Convert.ToDouble(dbResult)/1024;
Execute this SQL command, and it will reveal the disk-space usage of current database.
sp_spaceused
It also can be used to query the space usage of specific table. This link provides useful information about this problem.
To check the database size query:
sys.databases
Just query this, perhaps with C# or if you use SSMS (sql server management studio) shell, you can schedule a job that emails you or whatever you want.
Example:
SQL Server 2008: How to query all databases sizes?
Edit: NOT sure if error is thrown, it should log to event log or a sql log...
Side note:
Developer version is only $50 and holds same as Datacenter which hold 524 PB
http://technet.microsoft.com/en-us/library/cc645993%28v=sql.105%29.aspx
To Check the Size of the Database Two Ways:
/* new school way - data plus log and run in the local db that you want to see
here you can see the log and the mdf file.
*/
SELECT size*8.0/1024.0 as size_in_gb, *
FROM sys.database_files
GO
/* old school way, run for all db size*/
sp_helpdb
FYI - the MDF and NDF files are the only ones that attribute to the file size exceeding 10GB.
I am using the following method to calculate database current size crucial for comparing with sql size limitations:
public static int GetDbSizeInMB([NotNull] string connectionString) {
using (SqlConnection sqlConnection = new SqlConnection(connectionString)) {
sqlConnection.Open();
using (var sqlCommand = new SqlCommand()) {
sqlCommand.CommandType = CommandType.Text;
sqlCommand.CommandText = #"
SELECT SUM(CAST(FILEPROPERTY([name],'SpaceUsed') AS int)/128.0) AS [UsedSpaceInMB]
FROM sys.database_files
WHERE type_desc like 'ROWS' or type_desc like 'FULLTEXT'
";
sqlCommand.Connection = sqlConnection;
return Convert.ToInt32(sqlCommand.ExecuteScalar());
}
}
)
I have a T-SQL script to create a Database. I need to create this database runtime. When the application is Running.
What Connection String do I use?
How do I connect to the server and Create the Database? I am connecting to the server as a Network user. I am not using User "sa" I have a user "DBCreator"
My application is in C#.
I have this Script in T-SQL:
USE [master]
GO
CREATE DATABASE [XYZ]
-- Table Creation Code etc.
You can have two connection strings. One for master database to issue the CREATE DATABASE ... statement and another one for database created.
// You can use replace windows authentication with any user credentials who has proper permissions.
using (SqlConnection connection = new SqlConnection(#"server=(local);database=master;Integrated Security=SSPI"))
{
connection.Open();
using (SqlCommand command = connection.CreateCommand())
{
command.CommandText = "CREATE DATABASE [XYZ]";
command.ExecuteNonQuery();
}
}
// Quering the XYZ database created
using (SqlConnection connection = new SqlConnection(#"server=(local);database=XYZ;Integrated Security=SSPI"))
{
connection.Open();
using (SqlCommand command = connection.CreateCommand())
{
command.CommandText = "select * from sys.objects";
...
}
}
You can use the SMO objects to do that. I don't think i should explain what is already explained in details in a very good tutorial here
Definitely use SMO its intended to do everything that SSMS can do, and more! it actually has a command called Database.Create(), follow this MSDN page
after connecting to database in C#
string MyConString2 = "SERVER=localhost;" + "user id=mytest;" + "DATABASE=clusters;" + "PASSWORD=mypass;";
I have an algorithm which I need to after each run of algorithm that will fill the database, drop the database "clusters" of mysql manually and again connect to the empty database and run it again,gaining new data in tables
I want to make it automatically how can I drop or empty my database if exists in C# and then run my algorithm?
Here is example code that works and I think this is what you are talking about, if not, feel free to correct me.
using (var connection = new MySqlConnection("server=localhost;user=root;password="))
{
connection.Open();
var command = connection.CreateCommand();
command.CommandText = "drop schema if exists clusters";
command.ExecuteNonQuery();
command = connection.CreateCommand();
command.CommandText = "create schema clusters";
command.ExecuteNonQuery();
}
Prepare sql query for clearing your DB and test it in f.e. MySQL workbench. Following this, just execute it as you would execute regular query against DB in C#. One way is to clear all the tables in your database by using TRUNCATE statement and the second way is to DROP DATABASE and recreate it.
While I establish a connection to SQL Server using ADO.NET, it showing errors.
Following is the code:
SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;Initial Catalog=abdul;Integrated Security=true");
SqlCommand cmd = new SqlCommand();
con.Open();
String str="select * from emp where empname='Abdul'";
cmd = new SqlCommand(str, con);
SqlDataReader dr = cmd.ExecuteReader();
if (dr == null || !dr.HasRows)
{
MessageBox.Show("No Records found");
}
else
{
while (dr.Read())
{
textBox1.Text = dr[0].ToString();
textBox2.Text = dr[1].ToString();
}
}
When I am running the project it showing the following error:
Cannot open database "abdul" requested by the login. The login failed.
What have to do?
The login is successful at the the SQL Server level. Then either
the database exists but the login you are using doesn't have access to the database
the database doesn't exist
In SSMS, go to adbul database. Expand the security node and add the relevant users (which map to the login) + security there. If you still can't, have you created the database single user?
It's hard to give more details at the moment.
You need to check that the user you are connecting with is a valid SQL Login, and that the password supplied is correct. You also need to ensure the login has an associated SQL User in the database they are trying to connect to.
SQL Logins are used to access the server itself, and they are mapped to database SQL users.
You said you created the database. How did you do this? Was it from sql management studio? If so, was this in the same Windows session as you are executing the program code above?
I ask because if you could create a database, I believe you should be able to connect to it.
I'd look at the difference between successfully connecting with Sql Management Studio and trying to get past the 3rd line of code in your question. (assuming that's where it fails, maybe even edit the question to take out the lines beyond).
I am developing an ASP.Net website. I have to execute a query which fetches data from two different database.
I have two SqlConnection objects for these connections.
I have both the connections open. But in SqlCommand object, I can specify just one SqlConnection object.
SqlConnection conn = new SqlConnection("Data Source=xxx;Initial Catalog=xxx1;User ID=web_writeonly;Password=aaa;Network Library=DBMSSOCN");
SqlConnection conn1 = new SqlConnection("Data Source=xxx;Initial Catalog=xxx2;User ID=randomUser;Password=bbb;Network Library=DBMSSOCN");
conn.open();
conn1.open();
SqlCommand cmdUserInfo = new SqlCommand("<query goes here>", conn);
cmdUserInfo.Parameters.Add("#ifa", SqlDbType.NVarChar).Value = ifacode;
SqlDataAdapter sdaUserInfo = new SqlDataAdapter(cmdUserInfo);
sdaUserInfo.Fill(dtSummaryTbl);
conn.Close();
conn1.Close();
When I execute this code snippet, I get an error "The SELECT permission was denied on the object '*', database 'xxx2', schema 'dbo'."
Please help me out in sorting this problem.
Thanks!
That error means that you don't have sufficient permissions... check what sql login your website is associated with and then the permissions on the table you're trying to select data from.
Also, on closer inspection, one of your usernames is "web_writeonly"... kind of a hint if you're trying to do a select!!! ;)
Assuming your databases are on the same server why can't you just put your SQL into a stored procedure on one of the databases. I am pretty sure you can then just use one connection object and execute your stored procedure which gets data from two databases.