Explain the use of ExecuteNonQuery, ExecuteReader, ExecuteScalar?

ExecuteScalar is typically used when your query returns a single value. If it returns more, then the result is the first column of the first row. An example might be SELECT @@IDENTITY AS 'Identity'. ExecuteReader is used for any result set with multiple rows/columns (e.g., SELECT col1, col2 from sometable). ExecuteNonQuery is typically used for SQL statements without results (e.g., UPDATE, INSERT, etc.).

These are the methods under Command Object ExecuteReader : Used to execute SQL Select Command ExecuteScalar : Used to execute SQL Select command which is used to return a single value. Example the group function output ExecuteNonQuery : USed to execute SQL Insert, Delete and Update Commands.

ExecuteScalar-- ExecuteScalar returns only one value after execution of the query . it returns the first field in the first row. it is faster and convinient way when you wants rerive only single value at a time.

ExecuteReader- this method returns a DataReader which is filled with the data that is retrived using the coommand object . this is known as a forward only retrival of records.

ExecuteNonQuery- ExecuteNonQuery does not return any data at all. it is used basically to insert update operationas on table. means it is used for execution of DML commands e.g sqlcommand cmd=new sqlCommand("insert into emp values ('1','2'",con); con.open(); cmd.ExecuteNonquery();