Archive for the ‘MS SQL Server’ Category.

Back up and restore a single table with foreign keys using SQL Server

Today I needed to backup a single database table, then test a change to the data, then if the change failed, restore the original data.

Below is how I did this.

What I used

I used SQL Server Management Studio to do all of the following steps.
I performed the steps on a database running on a SQL 2012 database server.

Part 1 – Backup the table

SELECT *
INTO MyTable_Bak
FROM MyTable;

Note: This will work usually, however, it won’t work if you have a calculated column. If you have a calculated column, create the table first, then specify the columns you are inserting. I didn’t have a calculated column, so I didn’t take time to figure this out.

Part 2 – Restoring the table

Step 1 – Finding the Foreign Key Constraints

SELECT Name, Object_Name(parent_object_id) as [Table]
FROM sys.foreign_keys
WHERE referenced_object_id = object_id('MyTable')

The results were like this:

Name                    Table
FKDDED6AECAD1D93C0      MyOtherTable1
FK166B6670AD1D93C0      MyOtherTable2

Step 2 – Get the Drop and Create for each Foreign Key

In SQL Management Studio Express, I went to each table in the above list, and did the following:

  1. Locate the foreign key under Database | MyDb | Tables | dbo.MyTable | Keys.
  2. Right-click on the Foreign Key and choose Script Key as | Drop and Create to | Clipboard.
  3. Paste this into the query window.
  4. Delete the USING MyDb statement and separate the DROP statement from the two ALTER TABLE statements.
  5. Repeat for the next foreign key constraint, grouping the DROP statements and the ALTER TABLE statements together.

Step 3 – Run the DROP statements

Run the two DROP statements created above.

ALTER TABLE [dbo].[MyOtherTable1] DROP CONSTRAINT [FKDDED6AECAD1D93C0]
GO
ALTER TABLE [dbo].[MyOtherTable2] DROP CONSTRAINT [FK166B6670AD1D93C0]
GO

Step 4 – Restore the table

I used this query to restore the table from the backup.

SELECT * FROM MyTable
SET IDENTITY_INSERT dbo.MyTable ON; 
TRUNCATE TABLE MyTable ;
INSERT INTO MyTable (Id, Col1, Col2, Col3) -- Specify all columns here
SELECT (Id, Col1, Col2, Col3)              -- Specify all columns again here
FROM MyTable_Bak

Step 5 – Restore the foriegn key constraints

Run the ALTER TABLE scripts you grouped together from Step 2.

ALTER TABLE [dbo].[MyOtherTable2]  WITH CHECK ADD  CONSTRAINT [FKDDED6AECAD1D93C0] FOREIGN KEY([MyTableId])
REFERENCES [dbo].[MyTable] ([Id])
GO

ALTER TABLE [dbo].[MyOtherTable2] CHECK CONSTRAINT [FKDDED6AECAD1D93C0]
GO

ALTER TABLE [dbo].[MyOtherTable2]  WITH CHECK ADD  CONSTRAINT [FK166B6670AD1D93C0] FOREIGN KEY([MyTableId])
REFERENCES [dbo].[MyTable] ([Id])
GO

ALTER TABLE [dbo].[MyOtherTable2] CHECK CONSTRAINT [FK166B6670AD1D93C0]
GO

Conclusion

Your table is restored.

Observations

  1. This is a simple process for a table with only a few foriegn key constraints but could be difficult if you have dozens of foreign key constraints.
  2. Also, this process might not work perfectly with calculated columns without changes to the above process.
  3. It should be easier to do this.

If you know of a better way that doesn’t require $oftware, let me know.

SQL Addendum Table

I have an application I am building that needs to be malleable. It is a data-driven application. It will have users, contacts, organizations, and many other objects represented as a database table. One goal of this project is to allow for extension. Some customers are going to want to add a field to an object that our tables don’t include. We want to handle this end to end. It seems the perfect use of a property value table.

It would be pretty easy to create an Addendum table for each object.

dbo.Organization
dbo.OrganizationAddendum
dbo.User
dbo.UserAddendum

While that is OK, it requires additional work every time a table is created. What if a Partner writes a plugin and adds an object in the database? Well, unless the Partner creates an addendum table, this won’t really work.

Is there a way to solve this so any object in the database can have Addendum data?

I came up with this table.

CREATE TABLE [dbo].[LD_Addendum](
	[Id] [int] IDENTITY(1,1) NOT NULL,
	[Table] [nvarchar](100) NOT NULL,
	[TableId] [int] NOT NULL,
	[Property] [nvarchar](255) NOT NULL,
	[Value] [nvarchar](255) NOT NULL,
	[CreateDate] [datetime2](7) NOT NULL,
	[LastUpdated] [datetime2](7) NULL,
	[CreatedBy] [int] NOT NULL,
	[LastUpdatedBy] [int] NULL,
 CONSTRAINT [PK_Addendum_Id] PRIMARY KEY CLUSTERED 
(
	[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY])

Then in the Web interface, I could have single template control that works for any object. Whatever object I am editing, be it user, contact, organization or other, the control would exist. If a partner adds a plugin with a new object, the control would exist. Seems easy enough, right?

The problem comes in with some of the features that we would like to be automatically handled on the database side:

  1. Table should have Id column
  2. Table should have four main fields
    • Table <– Database table to add addendum data for
    • TableId <– The row of in the table that addendum is for
    • Property <– The property of the addendum
    • Value <– the value of the addendum data
  3. Table should have the four auditing fields in IAuditTable
    • CreateDate
    • CreatedBy
    • LastUpdated
    • LastUpdatedBy
  4. Only one Property of the same name should exist per table and id. Easily done with a Unique constraint.
  5. Table should have a constraint that enforces that table must exist.
    I found a way to do this: I created User-defined Function (UDF) and check constraint that uses the UDF.

    CREATE FUNCTION [dbo].[TableExists](@TableName NVARCHAR(255))
    RETURNS bit
    AS
    BEGIN
    RETURN ((SELECT COUNT(TABLE_NAME) FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = @TableName))
    END
    
  6. Table should have a constraint that enforces that TableId must exist in the Table
    1. Not supported – CLR UDFin C#? Or handle this in code?
  7. The row should delete when Table is deleted. Similar to ON DELETE CASCADE.
    • Not supported – CLR UDFin C#? Or handle this in code?
  8. The row should delete when a row from a table that matches Table and Id is deleted. Similar to ON DELETE CASCADE.
    • Not supported – CLR UDFin C#? Or handle this in code?

Perhaps we ignore the missing features from database side and handle them with code?

Or perhaps another database system other than Microsoft SQL Server (such as Postgresql) could do this?

Scaling

Assuming I got this to work, I see one main problem: Table size. However, I am not sure this is an issue. Tables can quite large, millions of rows. If this table got too big, then we could investigate why, analyze the table, and perhaps move a property value from the Addendum table to an actual column in a real table. This should replace the ability to create a plugin with an additional table, but it should make it so few plugins are needed as there is more extensibility out of the box.

Also, we found that default values often alleviate addendum tables. For example, imagine adding an addendum item to an organization, ContactIntervalInDays. Say a company is supposed to contact their customers every 90 days. However, some customers might require more or less contact. However, the default is 90. Instead of adding 90 to all customers, you set a default. If ContactIntervalInDays is not in the Addendum table, then use 90, otherwise use the value.

Anyway, it seems like an Addendum table is something that most projects and solutions, such as CRMs, Shopping Carts, ERPs, etc. should implement. It won’t solve the most complex issues with extending a product, but it would perhaps solve many of them. The more complex extension can continue to be added via a well-designed plugin architecture.

Unfortunately, this simplistic solution is not supported. The recommendation is to have 1 addendum table for every regular table. Ugh! That doesn’t scale and is not maintainable long term.

Still, I went ahead and requested this feature from the SQL team.

Entity Framework and many WHERE clauses

So today, I needed to get Entity Framework to return me a list of Products from the database based on a list of Product.Name and Product.Version values (not Ids). If it were Product.Id, it would have been simple as I could have used an IN statement, but it wasn’t.

The query might get many (maybe hundreds at a time) products based on the list. Here is the query I imagined.

So when doing a query like this, since there could be hundreds, I have a couple of options.

  1. Query the database once for each product.
    SELECT * FROM dbo.Product
    WHERE (Name = 'Product 1' AND Version = '10.0')
    

    Repeat this same query once for each Product.

  2. Query the database one time with an or clause for each Product.Name and Product.Version.
    SELECT * FROM dbo.Product
    WHERE (Name = 'Product 1' AND Version = '10.0')
       OR (Name = 'Product 2' AND Version = '10.0')
       OR (Name = 'Product 3' AND Version = '10.0')
       OR (Name = 'Product 4' AND Version = '1.0')
       -- There could be hundreds
    
  3. Query the database once and get all products and use code to find the ones I wanted.
    SELECT * FROM dbo.Product
    

Option 1
I didn’t like this option because I could end up doing hundreds of single queries. That doesn’t sound like a good idea. What would the performance impact would be when doing hundreds of single queries? The overhead of traversing over the network to the database would prevent this option from scaling.

Option 2
This is the option I imagined in my head. My gut said to use this option.

Option 3
This would work. We only have about two thousand products today and querying them all would, right now, not be bad at all. However, we just bought a company and will be adding more products. We plan to buy more companies. Also, we have two companies that we have already bought and have yet to add those products in. When would the number of Product rows in the database make the SELECT * and invalid option? Doing this would work now, but it leave a time bomb for some future developer encounter and have to fix.

Winner: Option 2

Problem
Entity Framework doesn’t really have an easy way to create the Option 2 query.

So, how do I create this query with many where statements?

Here are the two options I’ve found:

Inline SQL Query with Entity Framework

        private static List<Product> GetProductsByNameAndVersion(ActivationDbContext dbContext, IEnumerable<ProductRequest> products)
        {
            if (!products.Any())
            {
                return new List<Product>();
            }
            var query = "Select * FROM Product WHERE ";
            var or = "";
            var template = "(Name = '{0}' AND Version = '{1}')";
            foreach (var prod in products)
            {
                query += or;
                query += string.Format(template, prod.Name, prod.Version);
                or = " OR ";
            }
            var dbProducts = dbContext.Products.SqlQuery(query).ToList();
            return dbProducts.ToList();
        }

This option means I have to create magic strings and make sure that I handle the strings correctly. It has bugs already. Such as what if a product only has a name and not a version (version could be null or empty, who knows) or vice-versa? How would this affect my query string?

PredicateBuilder

Predicate Builder from the LinqKit library which is available as a NuGet package.

        private static List<Product> GetProductsByNameAndVersionPredicate(ActivationDbContext dbContext, IEnumerable<ProductRequest> products)
        {
            if (!products.Any())
            {
                return new List<Product>();
            }

            var predicate = PredicateBuilder.False<Product>();

            foreach (var prod in products)
            {
                var inner = PredicateBuilder.True<Product>();
                inner = inner.And(p => p.Name== prod.Name);
                inner = inner.And(p => p.Version == prod.Version);
                predicate = predicate.Or(inner);
            }
            var dbProducts = dbContext.Products.AsExpandable().Where(predicate).ToList();
            return dbProducts;            
        }

PredicateBuilder isn’t very intuitive. For starters, what is the different between these methods:

  • PredicateBuilder.True() – from what I understand this would be more appropriate and understandable as PredicateBuilder.And()
  • PredicateBuilder.False() – from what I understand this would be more appropriate and understandable as PredicateBuilder.Or()

Also, you have to remember to call AsExpandable() on the first call to a table in order to use it.

Conclusion

I am going to go with PredicateBuilder for now. It feels cleaner than rolling my own string query. But both solutions ultimately worked. That means that Entity Framework ultimately provided me a solution without an extra library. However, LinqKit saved me from magic strings. My only question is this: Why isn’t a predicate builder built into Entity Framework?

Add sql constraint on null, empty, or whitespace (C# string.IsNullOrWhiteSpace() equivelant)

Here is a User table. We wanted to make the UserName column not be null, empty, or whitespace.

So the constraint I made is this

ALTER TABLE [dbo].[User]  WITH CHECK ADD  CONSTRAINT [UserNameNotEmpty] CHECK  (([UserName]<>'' AND rtrim(ltrim(replace(replace(replace([UserName],char((9)),''),char((13)),''),char((10)),'')))<>''))
[UserName]<>''
Empty is checked first and not allowed.
replace([UserName],char((9)),'')
Replaces any instance a Tab character with an empty string.
replace([UserName],char((10)),'')
Replaces any instance a Carriage Return character with an empty string.
replace([UserName],char((13)),'')
Replaces any instance a Line Feed character with an empty string.
ltrim([UserName])
Left trim. It trims spaces from the left side of the string.
rtrim([UserName])
Right trim. It trims spaces from the right side of the string.

Note: You should know that char(9) is tab, char(10) is line feed, char(13) is carriage return.

Here is a complete User table. (This is a legacy system I inherited and I am fixing inadequacies.)

CREATE TABLE [dbo].[User](
	[UserId] [int] IDENTITY(1,1) NOT NULL,
	[UserName] [varchar](255) NOT NULL,
	[Password] [varchar](255) NOT NULL,
	[Salt] [varchar](255) NOT NULL,
	[FirstName] [varchar](255) NULL,
	[LastName] [varchar](255) NULL,
	[Email] [varchar](255) NULL,
	[Active] [bit] NOT NULL
 CONSTRAINT [PK_User] PRIMARY KEY CLUSTERED 
(
	[UserId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY],
UNIQUE NONCLUSTERED 
(
	[UserName] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
SET ANSI_PADDING OFF
ALTER TABLE [dbo].[User] ADD  CONSTRAINT [DF_User_Active]  DEFAULT ((1)) FOR [Active]
ALTER TABLE [dbo].[User]  WITH CHECK ADD  CONSTRAINT [UserNameNotEmpty] CHECK  (([UserName]<>'' AND rtrim(ltrim(replace(replace(replace([UserName],char((9)),''),char((13)),''),char((10)),'')))<>''))
ALTER TABLE [dbo].[User] CHECK CONSTRAINT [UserNameNotEmpty]

Notice, I don’t check null on the constraint, as NOT NULL is part of the UserName column design.

How to query a SQL database in C# using TableAdapters

Visual Studio has some great features to help you access the database and create objects for your database. You could manually create a connection string and manually create objects that represent the data in your database described here: How to query a SQL database in C#?. This article can show you how Visual Studio can do this for you.

So how is it done? By adding a Data Source.

Imagine you have a simple database for authentication with these tables:

User
- Id INT AUTOINCREMENT
- UserName VARCHAR(100)
- Password VARCHAR(MAX)
- Salt VARCHAR(MAX)

Person
- Id INT AUTOINCREMENT
- FirstName VARCHAR(255)
- LastName VARCHAR(255)
- Birthdate DATETIME
- UserId int FK to User.Id

Now imagine that you want to query these tables and use the data in your application.

Step 1 – Create a Visual Studio Project

  1. In visual studio create a new C# Console Application project.
  2. Once you have the project created, click on Project | Add New Data Source.
  3. Select Database and click Next.
  4. Select DataSet and click Next.
  5. Click New Connection and follow the wizard to connect to your database.
  6. Make sure that Yes, save the connection as is checked and give your saved connection a name and click Next.
  7. Click the checkbox next to Tables and click Finish.

This adds the following files to your project (the names might be slightly different on yours):

  • AuthDataSet.xsd
  • AuthDataSet.Designer.cs
  • AuthDataSet.xsc
  • AuthDataSet.xss

This code will add table adapters to your project. This basically does a lot of work for you and can save you a lot of potential development time.

Step 2 – Query a SQL Database using the Table Adapter

Now you can get the data from either of your tables with one line of code:

using System;
using System.Data;
using TableAdapterExample.AuthDataSetTableAdapters;

namespace TableAdapterExample
{
    class Program
    {
        static void Main(string[] args)
        {
            // Query the database (select * from Person) into a DataTable
            AuthDataSet.PersonDataTable table = new PersonTableAdapter().GetData();

            // Print out the table as proof.
            PrintDataTable(table);
        }

        /// How to print a DataTable
        private static void PrintDataTable(AuthDataSet.PersonDataTable table)
        {
            foreach (DataRow row in table.Rows)
            {
                foreach (DataColumn col in table.Columns)
                {
                    Console.Write(row[col].ToString().Trim() + " ");
                }
                Console.WriteLine();
            }
        }
    }
}

Hope that helps you.

How to execute a sql statement with a parameter in SQL Management Studio?

Today I got asked how to execute a parameterized SQL query in SQL Management Studio.

You can do it two ways:

Method 1 – Use SP_EXECUTESQL stored procedure to execute parameterized SQL

DECLARE @query NVARCHAR(MAX) = N'SELECT * FROM customer WHERE CustomerId = @id'
DECLARE @params NVARCHAR(MAX) = N'@id int';

EXEC SP_EXECUTESQL @query, @params, @id = 3;

If you need to do multiple parameters, it is pretty much the same syntax.

DECLARE @query NVARCHAR(MAX) = N'SELECT * FROM customer WHERE CustomerId IN (@id1, @id2)'
DECLARE @params NVARCHAR(MAX) = N'@id1 int, @id2 int';

EXEC SP_EXECUTESQL @query, @params, @id1 = 3, @id2 = 4;

Method 2 – DECLARE Variables to execute parameterized SQL

DECLARE @id INT = 3;
SELECT * FROM customer WHERE CustomerId = @id;

If you need to do multiple parameters, just declare another variable.

DECLARE @id1 INT = 3;
DECLARE @id2 INT = 4;
SELECT * FROM customer WHERE CustomerId IN (@id1, @id2);

How to export table data into a SQL insert script?

Have you ever had a table that you wanted to drop and recreate but you need all the data inside it. Perhaps it took you a lot of time to generate this data.

Well, you can save the data out as a SQL insert script if you want. Here is how:

  1. Open Microsoft SQL Server Management Studio and login.
  2. Right-click on the database and choose Tasks | Generate Scripts.
    Note: The first time you do this you will see and Introduction page. Click Next. You can click the check box next to Do not show this page again and you won’t see this screen.
  3. On the Choose Objects screen, click Select specific database objects.
  4. Expand Tables and click the check box next to the table you want to save and click Next.
  5. On the Set Scripting Options screen, click Advanced.
  6. Scroll down and under Types of data to script select Data only and click OK.
  7. Under File name select a file name to save to and click Next.
  8. Click Next, Next, Finish.

You now have a script to insert your data.

Using OSQL with Microsoft SQL databases

OSQL basic commands

Logging into a database with osql

c:\>osql -S [servername\instance] -U username [-P password]

Example1: Specifying the user and letting the command line prompt for a password.

c:\> osql -S Core\ldmsdata -U sa
password:

Example2: Specifying the user and the password.

c:\>osql -S ld87\ldmsdata -U sa -P pw

Example3: Using a trusted connection

c:\>osql -E

Show databases

1>
2>
select * from sysdatabases
go

Note: Or to see only the database Name row do the following:

1>
2>
select Name from sysdatabases
go

Creating a database

1>
2>
create database DatabaseName
go

Selecting a database

1>
2>
USE master
go

Drop a database

1>
2>
drop database DatabaseName
go

Show tables

1>
2>
1>
2>
USE DatabaseName
go
select * from INFORMATION_SCHEMA.TABLES
go

Note: Or to see only the Table_Name row do the following:

1>
2>
1>
2>
USE DatabaseName
go
select TABLE_NAME from INFORMATION_SCHEMA.TABLES
go

Drop a table

1>
2>
1>
2>
USE DatabaseName
go
drop table TableName
go

Insert a row into a table

1>
2>
1>
2>
USE DatabaseName
go
INSERT INTO TableName Values(“Column1value”,”Column2value”,”Column3value”)
go

Note: Or to insert by only providing values for a few columns and letting the other columns take the default values. This is useful when the first column is set to AUTO_INCREMENT.

1>
2>
1>
2>
USE DatabaseName
go
INSERT INTO TableName (Col2, Col3) Values(“Column2value”,”Column3value”)
go

Update a value in row of a table

1>
2>
1>
2>
USE DatabaseName
go
UPDATE TableName set ColumnName=’NewValue’ where SomeColumn=’whereValue’
go

Drop a view

1>
2>
1>
2>
USE DatabaseName
go
drop view ViewName
go

Backup a database

1>
2>
BACKUP DATABASE ulddb TO DISK=’c:\path\to\dbbackup.bak’ WITH FORMAT
go

You can do this at the command prompt with one single command:

c:\>osql -S ld87\ldmsdata -U sa -P pw -Q “BACKUP DATABASE ulddb TO DISK=’c:\path\to\dbbackup.bak’ WITH FORMAT”

Change the SA password with one line in a command prompt

c:>osql -E -S localhost\ldmsdata -d ULDDB -Q “sp_password NULL,’P@ssword’,’sa'”

I hope this helps you.

More Information

For more information see the following website:

  1. Administering SQL Server Using osql
  2. osql Utility

What is and how do I install the Northwind database?

The Northwind database is referenced online in sample code quite often. However, this renders the sample code useless to someone who doesn’t know what Northwind is or how to use it.

The Northwind database is basically just an example database that runs under SQL Server. This database is populated with data that represents an imaginary company’s sales data. It is a very common example database for SQL Server testing and sampling.

You might be wondering, what is SQL Server (though for your sake, I hope not). Well, SQL Server is Microsoft’s database software.

How do I know if SQL is installed?
If you have Visual Studio 2008 installed, you probably have SQL Server 2008 installed and you don’t even know it.

You can go to Add / Remove Programs and look for Microsoft SQL Server.

Or you can check for the services.

Or if you aren’t good with the GUI, you can open a command prompt and run this command to see if you have the SQL services:

C:\Users\UserName> sc query state= all |findstr SQL |findstr DISPLAY_NAME

DISPLAY_NAME: SQL Server (SQLEXPRESS)
DISPLAY_NAME: SQL Active Directory Helper Service
DISPLAY_NAME: SQL Server Agent (SQLEXPRESS)
DISPLAY_NAME: SQL Server Browser
DISPLAY_NAME: SQL Server VSS Writer

If you don’t see the services ouptut, you don’t have SQL Server Express installed. If you do have it, it is installed.

SQL Server is installed, now where do I get the Northwind Database?
Well, this was a struggle even for me. All the posts say the database creation script was installed with Visual Studio, but I sure don’t have any database creation scripts installed.

So I searched the web and Microsoft’s site for a while.

I finally found this link, but not until after about an hour of searching, hopefully this saves you some time.
http://www.codeplex.com/Wikipage?ProjectName=SqlServerSamples

So as of 3/4/2010, there was not “new” Northwind database, just and old one for SQL 2000. Which is fine because that old database is what most the sample code you find will be using.

I clicked on the Download link next to SQL Server 2000 Sample DBs.
I downloaded a ZIP file.
I extracted it.
I found the instnwnd.sql script among the extracted files.

How do I use the instnwnd.sql file to install the Northwind Database
This instnwnd.sql is nothing more than SQL script that will install the Northwind database for you. Well, you basically need your SQL server to run this script file and that is it.

If you have SQL Server Management Studio, just open it up and connect to your database, then File | Open the script and run it. But maybe you don’t know what SQL Server Management Studio is, let alone how to open it.

Sound easy right.

Well, everything sounds easy to some one who knows exactly how to do it, but if you don’t now how, it doesn’t sound easy. If you are among those that are hearing about this for the first time, let me help you.

Well, every server that has SQL Server installed has a command line tool installed called sqlcmd.exe. Hey, if I give you a command line you can run it, even if you don’t know what is really going on.

So just open a command prompt and run this command:

C:\Users\UserName> sqlcmd -E -i c:\path\to\instnwnd.sql

Changed database context to ‘master’.
Changed database context to ‘Northwind’.

Ok, the database installed now what?
Well, now you have the Northwind database installed.

From here you are one your own getting whatever sample code you have to connect to this database and compile.

How to execute SQL statement that has a single quote in C# or insert a row with a value that has a quote?

Imagine you have a query such as the following:

SELECT * FROM User WHERE LastName='O'Conner'

INSERT INTO User (FirstName, LastName, UserName, Email) VALUES ('John','O'Conner','jo'conner','joconner@somedomain.tld')

Well, that is obviously not going to work, because the apostrophe or single quote in the name O’Conner is going to break the query syntax.

You have to have two single quotes to use a quote.

SELECT * FROM User WHERE LastName='O''Conner'

INSERT INTO User (FirstName, LastName, UserName, Email) VALUES ('John','O'Conner','jo''conner','joconner@somedomain.tld')

Ok, so there are two ways to make sure you have two quotes in C#:

  1. You manage the query string yourself.
  2. You use a DataTable and let it manage the query string for you.

Managing the query string yourself

Ok, the answer is simple. You need two single quotes next to each other.

Now, when you have single string, this is easy to do. You need to replace each instance of a single quote with two single quotes using this function which already exists for you:

string.replace(string inStringToBeReplaced, string inNewString)

Here is an example of doing it wrong, then fixing it. Step through this in a debugger.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SingleQuoteInSQL
{
    class Program
    {
        static void Main(string[] args)
        {
            string FirstName = "John";
            string LastName  = "O'Conner";
            string UserName  = "joconner";
            string Email     = "joconner@domain.tld";

            // Both these queries are broken because of the space.
            string strQuery1 = "SELECT * FROM User WHERE LastName='" + LastName + "'";
            string strQuery2 = "INSERT INTO User (FirstName, LastName, UserName, Email) VALUES (" +
                        "'" + FirstName + "'," +
                        "'" + LastName + "'," +
                        "'" + UserName + "'," +
                        "'" + Email + "')";

            // This will actually break your query too, because it will replace valid single quotes
            // with two single quotes.  You need to do this on the actually data strings.
            strQuery1 = strQuery1.Replace("'", "''"); //
            strQuery2 = strQuery1.Replace("'", "''");

            // Replace any intance of a single quote with two single quotes, ''.
            // IMPORTANT: Typing two single quotes ('') is not the same as a double quote (").
            FirstName = FirstName.Replace("'", "''");
            LastName = LastName.Replace("'", "''");
            UserName = UserName.Replace("'", "''");
            Email = Email.Replace("'", "''");

            // Both these queries are working now;
            strQuery1 = "SELECT * FROM User WHERE LastName='" + LastName + "'";
            strQuery2 = "INSERT INTO User (FirstName, LastName, UserName, Email) VALUES (" +
                        "'" + FirstName + "'," +
                        "'" + LastName + "'," +
                        "'" + UserName + "'," +
                        "'" + Email + "')";
        }
    }
}

Using a DataTable to manage this for you automagically

This actually looks like more work at first, but really when handling a lot of data, it is much more easy to code using DataTables and DataRows.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;

namespace SingleQuoteInSQL
{
    class Program
    {
        static void Main(string[] args)
        {
            string FirstName  = "John";
            string LastName  = "O'Conner";
            string UserName  = "joconner";
            string Email        = "joconner@domain.tld";

            // Create the connection
            string mConnectionString = "Data Source=ServerName; user id=UserName; password=pw; Initial Catalog=DatabaseName;";
            SqlConnection mSqlConnection = new SqlConnection(mConnectionString);

            // Create a data adapter, this is what does the magic.
            String mQueryForSqlDataAdapter = "Select * from TableName";
            SqlDataAdapter tmpSqlDataAdapter;
            SqlCommandBuilder tmpSqlCommandBuilder;
            DataTable tmpDataTable = new DataTable();
            tmpSqlDataAdapter = new SqlDataAdapter(mQueryForSqlDataAdapter, mSqlConnection);

            // Use the SqlDataAdapter to create a table with the right schema but no data
            tmpDataTable = tmpSqlDataAdapter.FillSchema(tmpDataTable, SchemaType.Mapped);

            // Create a SqlCommandBuilder
            tmpSqlCommandBuilder = new SqlCommandBuilder(tmpSqlDataAdapter);

            // Create a DataRow and populate it
            DataRow row = tmpDataTable.NewRow();
            row["FirstName"] = FirstName;
            row["LastName"] = LastName;
            row["UserName"] = UserName;
            row["Email"] = Email;

            // Add this row to the DataTable
            tmpDataTable.Rows.Add(row);

            // Write this to the database
            tmpSqlDataAdapter.Update(tmpDataTable);
        }
    }
}

Notice we didn’t have to do a string replace of ‘ for ”.

How to restart the AUTOINCREMENT number for a table in Microsoft SQL 2008?

Ok, so I am in the middle of developing a database tool and so I populate a bunch of data, (by adding a bunch of rows), to a column that is AUTOINCREMENT.

So I have 3725 rows for a feature that is working. Now I am developing other features and debuggin them and so I want to reset the database to the same point it was before I started debugging.

So I am deleting all the rows above 3725, however my next AUTOINCREMENT number continues to go up.

I have this handy little SQL statement that should fix that:

To set the table back to 0.

DBCC CHECKIDENT (MyTable, RESEED, 0)

Now, if I set the table back to 0 that can be a problem if you still have rows in it.

The next row you try to insert will give you an error.

Msg 2627, Level 14, State 1, Line 1
Violation of PRIMARY KEY constraint ‘PK_Person’. Cannot insert duplicate key in object ‘dbo.Person’.
The statement has been terminated.

So if you have rows, try this:

DECLARE @size int
SET @size=(SELECT COUNT(*) From MyTable)
DBCC CHECKIDENT (MyTable, RESEED, @size)

Happy day, it works!!

Equivalent of mysqldump for Microsoft SQL Server 2008

There is a Database Publishing Wizard 1.1 you can download that may work for SQL Server 2005, but didn’t work for me with SQL Server 2008. However,Database Publishing Wizard 1.3 is installed with Visual Studio 2008 but I cannot find a separate download. This tool gets you the schema and data and everything but the “drop and create database” script.

So I think you need Visual Studio 2008 for this for SQL Server 2008 to get it. I am not sure why I cannot find it separately. Maybe Microsoft has a reason.

Step 1 – In Visual Studio 2008, go to Tools | Connect to Database and connect to a MS SQL database.

Under the Server Explorer window, the connection now appears.

Step 2 – Expand Data Connections.

Step 3 – Right-click on the connection and choose Publish to provider.

Step 4 – Click Next.

Step 5 – Choose the database.

Step 6 – Click Next.

Step 7 – Select the publishing options (such as to export the schema and data or just the schema).

Step 8 – Choose a file.

Step 9 – Click Finish.

Step 10 – The one thing this is missing is the script to drop and create the database. You can easily get this from Microsoft SQL Server Management Studio 2008 (there is a free Express version if you don’t have it). Just connect to the database, right-click on the database and choose Script Database as | Drop And Create to | Clipboard. Now past this text to the top of your file you just created.

What is the Microsoft SQL equivalent to MySQL's "Limit" feature in a SQL query?

Here is a MySQL Query

SELECT * FROM Table LIMIT 10

Here is a Microsoft SQL Query to perform the same

SELECT TOP10 * FROM Table

How to check if a SQL Table exists in C#?

Simple question, simple answer

SQL Query to return the data

SELECT TABLE_NAME FROM DBName.INFORMATION_SCHEMA.Tables WHERE TABLE_NAME='Article'

How do I check this in C#?

As for how you check that in C#? You just make sure the Row count returned from the query is 1. See this article I have already posted.

How do I get the number of rows returned from a Microsoft SQL Query in C#?

 

Return to ADO.NET and Database with C#

How to insert a row into a Microsoft SQL database using C#?

The following steps accomplishes this:

  1. Create a connection string.
  2. Create an insert query string.
  3. Create a SQLConnection object that uses the connection string.
  4. Create a SqlCommand object that used both the SQLConnection and the query string.
  5. Open the connection.
  6. Execute the query.
  7. Close the connection.
Steps are in the code with comments.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace InsertToDatabase
{
	public class InsertToDatabase
	{
		// Step 1 - Create a connection string.
		string connectionString = @"Data Source = ServerName; user id=UserName; password=P@sswd!; Initial Catalog = DatabaseName;";
		// Step 2 - Create an insert query string
		string query = "INSERT INTO Users (Firstname, Lastname, Email) VALUES ('Jared','Barneck','Jared.Barneck@somedomain.tld')";
		// Step 3 - Create a SQLConnection object that uses the connection string.
		SqlConnection connection = new SqlConnection(connectionString);
		// Step 4 - Create a SqlCommand object that used both the SQLConnection and the query string.
		SqlCommand command = new SqlCommand(query, connection);
		// Step 5 - Open the connection.
		connection.Open();
		// Step 6 - Execute the query.
		command.ExecuteNonQuery();
		// Step 7 - Close the connection.
		connection.Close();
	}
}