What exactly does cmd.ExecuteNonQuery() do in my program

string connection = "Provider=Microsoft.JET.OLEDB.4.0;Data Source=D:\it101\LoginForm\App_Data\registration.mdb";

string query = "INSERT INTO [registration] ([UserID] , [Name] , [Contact_no] , [City]) values (123, 'abc' ,12345, 'pqr')";

OleDbConnection con = new OleDbConnection(connection);
OleDbCommand cmd = new OleDbCommand();
cmd.CommandText = query;
cmd.CommandType = CommandType.Text;
cmd.Connection = con;

con.Open();
cmd.ExecuteNonQuery();

And what if i do not write cmd.ExecuteNonQuery() at the end of my program?
And if the query needs to be executed why is it written executeNonquery() instead of executeQuery()?

Answers:

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Method 1

if we want to deal with database two things will happen i.e; Modifying,Retrieving

Modifying:

In Modifying Section,we have Insert, Delete ,Update,…queries.so for this we need to use ExecuteNonQuery command.why because we are not querying a database, we are modifying.

syntax:

cmd.ExecuteNonQuery Method

Retrieving:

In this we query a database by using Select Statement.For this we use ExecuteReader(),ExecuteScalar()

If select Query return more than one record.we need to use ExecuteReader()

If select Query return only one record.we need to use ExecuteScalar()

syntax:

cmd.ExecuteReader() Method

cmd.ExecuteScalar() Method

The above statements(ExecuteReader(),ExecuteScalar(),SqlCommand.ExecuteNonQuery()) are used to execute command statement which you give in SqlCommand.If you dont use, your command not be executed.

Method 2

ExecuteNonQuery executes a query that is not expected to produce any results (e.g. an UPDATE, or INSERT).

ExecuteQuery executes a query that is supposed to produce a result (i.e. a SELECT).

If you do not write ExecuteNonQuery at the end, your query won’t be executed.

Method 3

SqlCommand.ExecuteNonQuery Method

Executes statement against the connection and returns the number of rows affected.
For UPDATE, INSERT, and DELETE statements, the return value is the number of rows affected by the command.

executeQuery Method

Runs the given SQL statement and returns a single SQLServerResultSet object.

If you want to execute your query you should use ExecuteNonQuery

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