Posts Tagged ‘SQL’

Recently in one of my Virtual Machine (VM)s I received the above error message when trying to connect to a SQL Server which I used to connect on other times.

image

After having a look I found that the trust between my virtual machine and the domain was broken. You can find the status of the secure channel by using the PowerShell command Test-ComputerSecureChannel.

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This will also be evident when you try to login to the computer using a domain account. It will generate the following message.

image[6]

To fix this you can try using the below methods.

1. PowerShell

Use the command Test-ComputerSecureChannel.

If your current login has the required access in the domain you can use the below command.

Test-ComputerSecureChannel –Repair

If you need to use another account than the current logged user then you need to use the –Credential parameter when calling the command.

Test-ComputerSecureChannel –Repair –Credential MyDomain\MyUser

2. Joining the domain again.

This will also get fixed by removing the machine from the domain and adding it back. Before removing the computer from the domain make sure you have access to a local administrator account on the computer. Otherwise you will not have a way to login to the computer.

This can be achieved by going to computer system properties,

  1. removing the computer from the current domain,
  2. restarting the computer.
  3. adding the computer to the domain again
  4. restarting the computer

To avoid the two restarts you can try using the following PowerShell commands.

$myPC = Get-WmiObject Win32_ComputerSystem
$myPC.UnjoinDomainOrWorkGroup("Account Password", "Account Username”, 0)
$myPC.JoinDomainOrWorkGroup("Domain", "Account Password", "Account Username", $null, 3)
Restart-Computer -Force

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.

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By now as you know, in this post I am going to discuss about two SQL commands we use regularly to clear data in our tables.

Usage

  1. DELETE FROM TABLENAME
  2. TRUNCATE TABLE TABLENAME

Even though they do a similar thing, there are some differences which makes them unique commands.

 

DELETE

TRUNCATE

1. Considered as Data Mining Language (DML) statement. Considered as Data Definition Language (DDL) statement.
2. Can be used to delete all or part of data in a table. Will delete all the data in a table.
3. Will log the actions. There will be no logging on record deletion.
4. Will use more locks. Will use fewer locks.
5. Will use more resources. Will use less resources.
6. Slow. Fast.
7. Will not reset the identity seed. Will reset the identity seed to 0.
8. Can be used to delete data in tables having relationships. Cannot use in tables having relationships.
9. Can be used in tables involved in log shipping or replication. Cannot be used in tables involved in log shipping or replication.
10. Transaction can be rolled back. No rollback.
11. Table may keep the empty pages. Can be released by running, SHRINKDATABASE (Database Name). Data pages related to the table will be de allocated and returned to the system.
12. Related Triggers are fired. Triggers are not fired.

 

If you used DELETE to fully remove all the records, you can reset the identity value by running the following command.

  1. DBCC CHECKIDENT (TABLENAME, RESEED, 0)

If you do have some rows left in table, simply replace 0 with the last identity column value. For example if you put 5 instead of 0 then the next record inserted into the table will have an identity column value of 6.

If you jus need to check the current identity value just use the following command.

  1. DBCC CHECKIDENT (TABLENAME, NORESEED)

Importing Data into SQL

Posted: September 30, 2012 in SQL Server
Tags: , , ,

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.

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.

If you are into programming you should have definitely worked with calculated fields in SQL. But for others I will briefly explain what they are.

Calculated columns are columns which depend on other columns. It gets its value by calculating which can involve values of other columns. The calculation formula is the only thing stored in the column.

So each time the column is referenced the calculation is done. But if you use the keyword “persisted” while creating the column then the values will be kept in the table. Whenever a referenced value is updated the computed column is also automatically updated to highlight the change. Also by using persisted you can index a computed column.

You can create a table with persisted computed column as follows.

  1. CREATE TABLE Customer
  2. (
  3. CustomerId INT IDENTITY(1, 1) NOT NULL,
  4. CustomerFirstName NVARCHAR(100) NOT NULL,
  5. CustomerLastName NVARCHAR(100) NOT NULL,
  6. CustomerFullName AS CustomerFirstName + ' ' + CustomerLastName PERSISTED
  7. )

One thing to remember is that you cannot directly insert values to a computed column.

I think you got a basic idea of computed columns. Now I would like to show how to create a computed column dynamically. For example think that you need to add a computed column to a table using a stored procedure. It is not a big deal.

I need to insert a TotalOrder column to the table named FoodOrder.

  1. CREATE TABLE FoodOrder
  2. (
  3. OrderId INT IDENTITY(1, 1) NOT NULL,
  4. OrderDate SMALLDATETIME NULL,
  5. CustomerName NVARCHAR(100) NOT NULL,
  6. TotalStarter INT NULL,
  7. TotalMainCourse INT NULL,
  8. TotalSoftBevarage INT NULL,
  9. TotalLiquer INT NULL,
  10. TotalDessert INT NULL
  11. )

This can be done using the following query.

  1. DECLARE @sExecuteCommand VARCHAR(250), –Keepa the command to be executed.
  2. @sColumns VARCHAR(150) –Keeps the columns to be included in the formula.
  3.  
  4. SET @sColumns = 'TotalStarter+TotalMainCourse+TotalSoftBevarage+TotalLiquer+TotalDessert+'
  5. SET @sExecuteCommand = 'ALTER TABLE FoodOrder ADD TotalOrder AS ' + SUBSTRING(@sColumns, 1, LEN(@sColumns)-1) — Creating the computed column.
  6. EXEC (@sExecuteCommand)

Note that a cursor or a loop can be easily used to populate the variable “sColumns” with the columns required for the formula.

Hope this helps.