All Basic SQL Queries for Database Server & Visual Studio in C#

This article will help you understand the syntax for basic queries that are most used in SQL Server. In the first part we will list down important queries that you need to understand & then in second part we will see how we can use these queries in Projects in Visual Studio using C# Programming Language.

Before We Start

Since these queries will be run against a Database, you should first create a database if you don’t have it already. Follow these steps to create a database.

  1. Right click on Databases & click on New Database.
  2. Add Tables in Database.
  3. Then Put Columns in these Tables.

Below is a Screenshot of Database I created. You can create it like this if you want the same columns & datatypes.

Part 1 : Most used SQL Queries

Below is the List of Important queries. I have commented them so you can understand them easily. Copy each of them one by one & run them in your SQL server on a sample database such as North Wind. This will help you to practically understand them.

Once you have tried the above queries in SQL server, we can now move on to Part 2.

Part 2 : Using SQL Queries in Projects

We develop our projects mostly through Visual Studio. I prefer to use C# Programming language because I am good at it but you can use language that you are comfortable with.

I created a class named Query. Where I put my important methods as follows.

Now I will create an object of this class anywhere I want to use queries. I will pass my Query & Database Path to the methods from this object. Below is the example where I am passing Insert query & Database to this object.

Here Customer ID, Invoice ID, Date etc are my values which i am going to store. ( q ) is the object of Query class & Connect is the method of Query Class written in the First Step. Here ( path ) is the path of Your SQL Database. My path is this.

string path = @"Data Source=.sqlexpress;Initial Catalog=Invoicer;Integrated Security=True";

Here is another Example that demonstrate Updating a record.

Similarly for Deleting a record.& Lastly Checking the Record.

In above examples CustomerDetails is my table name where as CustomerID, CustomerName & CustomerAddress are the column names of my table. You can see I am setting their values like

"+CustomerID+' ,  ' "+CustomerName+' & ' "+CustomerAddress+'

in queries. These value have to be specified in your code either from initializing them or by getting their values from Console or Windows Form GUI.

Remember

These queries are for beginners & you can use them in your practice work however If you are developing an app for a client you should learn more. Here are some handy guidelines that you should follow.

  • Use parameterized queries.
  • Use stored procedures
  • Use Hashing if data is important

There are tons of other guidelines but that would be out of scope for current topic. That’s all for now. I hope you now have basic understanding of these queries & their use. Ask questions if you have any misconception.



Comments

  1. Sam.. i am not SQL queries teacher. (p) . I only give idea here about the queries we use used in Visual Studio. & for SQL Database i give examples here basic & mostly used . & if you are intelligent enough you can easily use them in VS.

  2. ประภัสสร. Great to hear that it helped you. (h) … plz can you elaborate what you are asking about. ? . i have complete documentations & examples …ask anything. & i will tell you about it… :p

  3. You have left some of the important ones but i will manage it. I am in 2nd semester.

    Sami Yousuf

  4. wow! thx!
    Sorry for taking to long, i just wanna try to do my best first! Hahaha.>>And Now! i really get stuck!
    1. my datatype is text .
    2. i want to count on (ProQty) that less than (ProWarn).
    i try string sql = "select COUNT(ProductID) from Product where ProQty <= ProWarn";
    cmd = new OleDbCommand (sql);
    and so on…..
    but it count only ProductQty greater than ProWarn
    thx you for ur help;

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Sajjad Arif Gul

Hi! I am Sajjad Arif Gul, Software Engineer, Web & Mobile Developer from Karachi Pakistan. I love sharing my knowledge that could possibly help someone’s life in some capacity. Happy Coding.