Finding Number of Records in SQL Tables

By using the following query you will be able to get all the tables with at least one record in the selected database. It will be handy when you needed to get an idea of the number of records in a database. This uses two SQL Server system views, namely SysObjects and SysIndexes.

1. SELECT sysobjects.name AS [Table Name],
2.         MAX(sysindexes.rows) AS [Number of Records],
3.         sysobjects.crdate AS [Created Date],
4.         sysobjects.refdate AS [Referenced Date]
5. FROM sysobjects
6. INNER JOIN sysindexes ON sysobjects.id = sysindexes.id
7. WHERE sysobjects.xtype = 'U' -- Filtering all the User Tables.
8.     AND sysindexes.rows > 0 -- Getting all the tables having at least one reoord.
9. GROUP BY sysobjects.name,
10.     sysobjects.crdate,
11.     sysobjects.refdate
12. ORDER BY 2 DESC -- Ordering by the number of records in table.

 

Above query will bring the following results on the Northwind database.

Importing Data into SQL

If you need to import data from a file, this can be achieved by using SQL Bulk Insert command. Recently I did use this method to import some 500 000 data from few comma separated value (CSV) files and thought to share it with you. What you need to remember is, if you are importing data from more than one file the data should have the same format through out the files.

This is a sample set of data I imported into my table from the file named File1.csv.

Login,Name,Date,Result,Pass

U0001,Roman Silva,1/10/2010 17:23,100,TRUE

U0002,Anthony Don,28/09/2010 10:01,70,TRUE

U0003,Saman Perera,16/09/2010 11:31,90,TRUE

U0004,Silvia Raz,26/09/2010 22:11,40,FALSE

U0005,Rebecca Maine,18/09/2010 11:30,100,TRUE

I used the following script to create a temporary table for my imported data.

1. SET ANSI_NULLS ON
2. GO
3.  
4. SET QUOTED_IDENTIFIER ON
5. GO
6.  
7. CREATE TABLE [dbo].[TABLENAME_ImportedData](
8.     [LoginId] [NVARCHAR](50) NOT NULL,
9.     [Name] [NVARCHAR](200) NULL,
10.     [Date] [DATETIME] NULL,
11.     [Result] [INT] NULL,
12.     [Pass] [NVARCHAR](8) NULL
13. ) ON [PRIMARY]
14.  
15. GO

To fetch data from the file I used the following script.

1. BULK INSERT [TABLENAME_ImportedData]
2. FROM 'D:\DataFiles\File1.csv'
3. WITH (
4.          FIELDTERMINATOR =',', -- Since my columns are seperated using commas (,).
5.          ROWTERMINATOR ='\n',  -- Since each data row is in its own line.
6.          FIRSTROW = 2          -- Since my first row is having column names. Please note FIRSTROW is not recommended to skip the column names.
7.       )

While running the script I faced an issue with the date since my server was set to US English as the default language. In US English the dates should be in MDY format. So I had 3 choices, either to change the date formats on my data files, change the server default language to another language which has its date format as DMY or change the date format of the server. I used the easy way to change the date format of the server by running  the following command.

1. SET DATEFORMAT dmy

If you like to change SQL server default language and need help please read my article on that.

Changing SQL Server Default Language

If you needed to change the default language of a SQL Server login you can do so by using sp_defaultlanguage command.

First determine the current default language by using the @@language variable as follows.

1. SELECT @@language

Then choose the language you want to change to from the available languages. You can find the available languages by the following command.

1. EXEC sys.sp_helplanguage

After selecting the language wanted to change, run the following command to change the default language, I am changing it to British using the following command.

1. DECLARE @Login NVARCHAR(30)
2. SET @Login = SYSTEM_USER
3. EXEC sp_defaultlanguage @Login, 'British'

Run the @@language to see whether the default language is changed as you wanted. Do not forget to use a new query window to see the changes.

Creating Database Table and Moving Data

When the need comes to port tables from one server / database to another server / database there is an easy way than creating the tables manually and importing data into table.

 

By using the following query you can import the table structure and the data of the required table.

1. SELECT *
2. INTO [DestinationServerName\SQLServerInstanceName].[DestinationDatabaseName].[OwnerName].[DestinationTableName]
3. FROM [SourceServerName\SQLServerInstanceName].[SourceDatabaseName].[OwnerName].[SourceTableName]

 

Using the above method you can transfer tables between different databases, Server instances or different database servers.

Consider the following example in which I am transferring the Customers table from Northwind database to my Test database.

 

1. SELECT *
2. INTO [Test].[dbo].[Customers]
3. FROM [Northwind].[dbo].[Customers]

 

Here SELECT statement will behave the same way as in a normal SELECT * FROM TableName statement meaning you can use all the techniques used in SELECT statements to filter the data needed to be ported. For example following query will only bring customers who are from UK.

1. SELECT *
2. INTO [Test].[dbo].[Customers]
3. FROM [Northwind].[dbo].[Customers]
4. WHERE Country = 'UK'

 

One thing to remember is, this method will not import the keys, meaning if you had a primary key set to CustomerId it will not exist in your new table. So you need to add the keys (primary and secondary) to the new table to match it with the source table. If you had identity specification turned on in your source table this will set it for you, so you do not need to set it again.

UPDATE with JOIN

If you need to update data of a table (DestinationTable) with data of another table (SourceTable) there are 3 ways you can get this done in SQL.

Method 1

This is the most common and simple way with using a sub query.

1. UPDATE DestinationTable SET DestinationColumn =
2.     (SELECT ValueColumn FROM SourceTable WHERE DestinationTable.MappingColumn = SourceTable.MappingColumn)

 

Method 2

This users the most common FROM clause to join the two tables as shown below.

1. UPDATE DestinationTable SET DestinationColumn = SourceTable.ValueColumn
2. FROM SourceTable
3. WHERE DestinationTable.MappingColumn = SourceTable.MappingColumn

 

Method 3

Last method mentioned below uses the join clause to join both the tables to make the update happen properly.

1. UPDATE DestinationTable SET DestinationColumn = SourceTable.ValueColumn
2. FROM DestinationTable
3. INNER JOIN SourceTable ON DestinationTable.MappingColumn = SourceTable.MappingColumn

 

Hope these helps.

Database Not Accessible

Recently after restoring a database backup which I got from another server I repeatedly encountered an error when logged in using a user who is given permission. But when ‘sa’ account is used I could work with the database without any problem.

The error message was “The database DATABASE NAME is not accessible. (ObjectExplorer)” which was not helpful since it didn’t give any clue to figure out the issue.

Later I found that the issue is because the user in the restored database is not properly mapped to the user in the new server and the resolution for this is to run the stored procedure sp_change_users_login to correct the orphaned user.

• sp_change_users_login 'update_one', 'USER', 'LOGIN' – Links the given user in the current database to the specified login.
• sp_change_users_login 'auto_fix', 'USER' – Links the given user in the current database to the login having the same name in the current server.

After running this you will be able to access the restored database without any issue using the mentioned database user.

Saving Table Changes in SQL Server 2008 R2

Have you noticed that with the default settings of SQL Server 2008 R2 you cannot use the design view to edit and save table changes which requires table to be recreated. But if you used earlier SQL Server installations you should remember that this functionality was possible. When you try to save such a table you will see an error similar to the following in SQL Server 2008 R2.

But the good news is that we can enable this functionality by going to SQL Server options.

Click Tools –> Options and expand Designers node and select ‘Table and Database Designers’.

Then uncheck the option ‘Prevent saving changes that require table re-creation’ and press OK.

Now if you try to save the table changes SQL will do the alteration without any complains.

Repairing a Corrupted Database

When we are regularly using databases, sometimes those will get corrupted. This happened to one of my applications, it was a Windows Mobile application with SQL Server CE database. Since it is running in a mobile it is bit difficult for us to fix the database using the desktop machine. I used the following .Net Compact framework code to fix the corrupted database while the database is in the mobile.

1. private void btnRepair_Click(object sender, EventArgs e)
2. {
3.     Cursor.Current = Cursors.WaitCursor;
4.     Cursor.Show();
6.     // txtDBPath will contain the path to the database.
7.     engine = new SqlCeEngine(@"Data Source=" + txtDBPath.Text + ";Password=DBPassword");
8.     try
9.     {
10.         if (!engine.Verify())
11.         {
12.             Cursor.Current = Cursors.Default;
13.             Cursor.Hide();
15.             DialogResult result = MessageBox.Show("Database is corrupted. Do you want to repair?", "My App", MessageBoxButtons.YesNo, MessageBoxIcon.Question, MessageBoxDefaultButton.Button1);
16.             if (result == DialogResult.Yes)
17.             {
18.                 Cursor.Current = Cursors.WaitCursor;
19.                 Cursor.Show();
21.                 // You can also use RepairOption.DeleteCorruptedRows.
22.                 engine.Repair(null, RepairOption.RecoverCorruptedRows);
24.                 Cursor.Current = Cursors.Default;
25.                 Cursor.Hide();
27.                 MessageBox.Show("Database repaired successfully.", "My App");
28.             }
29.         }
30.         else
31.         {
32.             Cursor.Current = Cursors.Default;
33.             Cursor.Hide();
34.             MessageBox.Show("Database is not corrupted.", "My App");
35.         }
36.     }
37.     catch (Exception ex)
38.     {
39.         Cursor.Current = Cursors.Default;
40.         Cursor.Hide();
41.         MessageBox.Show(ex.Message, "Error!");
42.     }
43. }

Next time you get a corrupted SQL CE database try it out.

Connecting to MySQL in Visual Studio 2010

If you need to access MySQL databases using Visual Studio you have to install MySQL connector into your machine.

Currently only mysql-connector-net-6.3.1 is supporting Visual Studio 2010 which is still an alpha product.

To download it, use this link and switch to Development Releases tab.