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Welcome all! This is a second part of my SQL in C# tutorial series. If you are interested in writing INSERT commands then take a look at part 1: INSERT into table. In this tutorial I would like to show you how to read several records by using a SELECT statement, and how to delete records by using DELETE statement. Enjoy this short tutorial.
![]() Reading records with SQL SELECT statment: using SqlDataReader class So, so far we created a database, with a table for numbers and descriptions, and added a record. Remember, table NumbersTable has two columns, numbers and description. During insertion and deletion column names are not used, you need only their order. So when you write some code, take a look again at the table. If you make it wrong then god help you with debbuging. Code:
SqlConnection connection1 = new SqlConnection(
Properties.Settings.Default.some_numbersConnectionString);
SqlCommand insertCommand = new SqlCommand(
"INSERT into NumbersTable values (1002, 'will delete this one')",
connection1);
connection1.Open();
insertCommand.ExecuteNonQuery();
connection1.Close();
MessageBox.Show("Record inserted. Please check your table data. :)");
For a start you need a SqlConnection and SqlCommand classes. They are required for any SQL statement. This time however, we could also use a SqlDataReader class. It fetches the received data and lets you access them one record at a time. After calling reader = selectCommand.ExecuteReader(), you are able to access your records one-by-one. By turns, call reader.Read() while checking are there any more records to read. If it returns false then you are done with reading. Then process the current record by reading reader[0], reader[1] and so on. Again, field order is important. Try hard to avoid making mistakes here. Code:
SqlConnection connection1 = new SqlConnection(
Properties.Settings.Default.some_numbersConnectionString);
SqlCommand selectCommand = new SqlCommand(
"SELECT * FROM NumbersTable",
connection1);
connection1.Open();
SqlDataReader reader = selectCommand.ExecuteReader();
string fetchedRecords = string.Empty;
while (reader.Read() == true)
{
fetchedRecords += "Record: (number) " + reader[0] + " (descriptio) " + reader[1] + " \n";
}
connection1.Close();
MessageBox.Show("Found following records: \n \n" + fetchedRecords);
![]() Deleting several records: SQL DELETE statement Well, deletion is as easy as a pie. There is nothing more than the short code below. Note that you can use several conditions, but ntext and varchar field types do not play with equal-to operator (=). That is why the other version is commented out. Code:
SqlConnection connection1 = new SqlConnection(
Properties.Settings.Default.some_numbersConnectionString);
SqlCommand insertCommand = new SqlCommand(
"DELETE NumbersTable WHERE number = 1002",
//"DELETE NumbersTable WHERE number = 1002 AND description = 'will delete this one'",
connection1);
connection1.Open();
insertCommand.ExecuteNonQuery();
connection1.Close();
MessageBox.Show("Record 1002 deleted. Please check your table data again. :)");
![]() Thank the author, share some reputation points I would like to thank everyone, especially Jordan and Siten, that were supporting me. Writing tutorials is a hard work. If you want to leave a comment or +rep my post then go ahead. I thank you in advance. ![]()
__________________
proudly presenting my personal website and game website: F1Simulation. a thrilling Managed DirectX racing game... also my Ask Me look at my tutorials about cropping images and Mono: bundling Mono with programs and lambda expressions |
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Re: Writing SQL commands in C# - Part 2 - Reading and deleting records
Wow, very nicely done! I enjoy reading your tutorials and will continue to support you. +rep!
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Re: Writing SQL commands in C# - Part 2 - Reading and deleting records
+rep
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CodeCall Blog | CodeCall Wiki | Shareware Programming is a branch of mathematics. My CodeCall Blog | My Personal Blog |
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Re: Writing SQL commands in C# - Part 2 - Reading and deleting records
Thank you all three. I appreciate your comments a lot. Thanks to you I achieved a Guru status, too. *hurray*
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__________________
proudly presenting my personal website and game website: F1Simulation. a thrilling Managed DirectX racing game... also my Ask Me look at my tutorials about cropping images and Mono: bundling Mono with programs and lambda expressions |
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| Tags |
| arek bulski, c# code, sql delete, sql select |
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