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Table Valued Parameters in SQL Server:Question and Answer

Q.1. What are Table Valued Parameters?

Ans: Table-valued parameters (TVPs) allow you to transfer a complete set of rows as a single parameter to stored procedures in T-SQL and user-defined functions (UDFs). TVPs facilitate the transfer of a set of rows between your .NET client and SQL Server database in a single roundtrip using a single stored procedure call, making them a powerful feature.

The foundation of a TVP is a user-defined table type that you create to specify the schema for a collection of rows. TVPs can be compared to other "set" constructs, such as table variables, temporary tables, and Common Table Expressions (CTEs), as they all offer a source of tabular data that can be queried and manipulated.

Q.2. What are Its Benefits?

Ans: The benefits of TVPs include:

  • TVP data is always kept in tempdb, and SQL Server automatically manages the cleanup when the TVP is no longer needed, abstracting direct interactions with tempdb.
  • TVPs allow you to transfer an entire table (set of rows) between stored procedures and UDFs as a single parameter, reducing roundtrips and improving performance.
  • TVPs provide reusability as they have centrally maintained schemas, unlike table variables, temporary tables, and CTEs.
  • TVPs are particularly useful for bulk data operations, like bulk inserts and updates.

Q.3. How to Create a User-Defined Table Type?

Ans: To create a user-defined table type, use the 'CREATE TYPE' statement with the 'AS TABLE' clause. This example shows how to create a table type called CustomerUdt with three columns:

CREATE TYPE CustomerUdt AS TABLE
(
    Column1 DataType1,
    Column2 DataType2,
    Column3 DataType3
);

Q.4. Where can You Watch The TVP?

Ans: In SQL Server Management Studio's Object Explorer, you can find TVP types displayed in the User-Defined Table Types node under Programmability

Image: User-defined table types that can be utilized for TVPs displayed in SQL Server Object Explorer

Q.5. How to Create a Single Stored Procedure With TVP?

Ans: You can create a single stored procedure that utilizes TVPs by declaring TVP variables as parameters. Here's an example using two TVPs (one for order rows and the other for order detail rows):

CREATE PROCEDURE YourStoredProcedureName
    @OrderTVP OrderUdt READONLY,
    @OrderDetailTVP OrderDetailUdt READONLY
AS
BEGIN
    -- Your code to handle the TVPs and perform operations
END

Q.6. How to Use TVP for Bulk Inserts?

Ans: TVPs are particularly useful for bulk inserts. You can insert multiple rows into a table using TVPs. Here's an example of a stored procedure that accepts a TVP and inserts each row into the Product.Location table:

CREATE PROCEDURE YourBulkInsertProcedure
    @Locations LocationUdt READONLY
AS
BEGIN
    INSERT INTO Product.Location (LocationName, CostRate, Availability, ModifiedDate)
    SELECT LocationName, CostRate, 0, GETDATE()
    FROM @Locations;
END

Q.7. How to Use TVP for a Bulk Update?

Ans: TVPs can also be used for bulk updates. You can join a TVP with a table and create an UPDATE statement to update matching rows. Here's an example:

CREATE PROCEDURE YourBulkUpdateProcedure
    @Updates UpdateTVP READONLY
AS
BEGIN
    UPDATE TargetTable
    SET TargetColumn = UpdateTVP.NewValue
    FROM TargetTable
    INNER JOIN @Updates AS UpdateTVP
    ON TargetTable.ID = UpdateTVP.ID;
END

Q.8. How can One Pass Multiple Rows of Data from a Client's Application to an SQL Server Using ADO.NET?

Ans: To pass multiple rows of data from a client's application to SQL Server using ADO.NET, you can use Table-Valued Parameters (TVPs). Here's an example of passing DataTable objects as TVPs:

using (SqlConnection connection = new SqlConnection("YourConnectionString"))
{
    connection.Open();


    using (SqlCommand command = new SqlCommand("YourStoredProcedure", connection))
    {
        command.CommandType = CommandType.StoredProcedure;


        // Add TVP parameters to the command
        SqlParameter tvpParameter = command.Parameters.AddWithValue("@TVPName", yourDataTable);
        tvpParameter.SqlDbType = SqlDbType.Structured;


        command.ExecuteNonQuery();
    }
}

Q.9. How to Pass a Connected Data Source as a TVP to an SQL Server?

Ans: You can use any object derived from DbDataReader (a connected data source) to stream rows of data to a TVP. Here's an example of passing a connected OracleDataReader source to SQL Server as a TVP:

using (SqlConnection connection = new SqlConnection("YourConnectionString"))
{
    connection.Open();


    using (SqlCommand command = new SqlCommand("YourStoredProcedure", connection))
    {
        command.CommandType = CommandType.StoredProcedure;

Q.10. How to Pass Collections to TVP Using Custom Iterators?

Ans: You can pass collections to TVPs by having your collection class implement the IEnumerable interface. This allows ADO.NET to use the custom iterator method to transfer data to TVPs. Here's an example:

  // Add TVP parameter to the command
        SqlParameter tvpParameter = command.Parameters.AddWithValue("@TVPName", yourDataReader);
        tvpParameter.SqlDbType = SqlDbType.Structured;


        command.ExecuteNonQuery();
    }
}


public class YourCollection : List, IEnumerable
{
    public IEnumerator GetEnumerator()
    {
        // Custom iterator implementation to map collection items to SqlDataRecord
        foreach (var item in this)
        {
            SqlDataRecord record = new SqlDataRecord(
                new SqlMetaData("Column1", SqlDbType.Int),
                new SqlMetaData("Column2", SqlDbType.NVarChar, 50)
                // Add more columns as needed
            );


            record.SetInt32(0, item.Column1);
            record.SetString(1, item.Column2);
            // Set other column values as needed


            yield return record;
        }
    }


    // Implement other interfaces as required
}

Q.11. Explain How The Collection Classes Implement The Custom Iterator Needed to Support TVPs?

Ans: The collection classes implement a custom iterator by providing a GetEnumerator method that returns an IEnumerator. This method is used by ADO.NET to retrieve each element from the collection and convert it into a SqlDataRecord object representing a row in the TVP.

The custom iterator method maps the properties of each object in the collection to the columns specified in the user-defined table type of the TVP. It sets the values of each column in the SqlDataRecord using the corresponding properties of the object. The yield return statement is used to transfer each SqlDataRecord to the server's pipeline one at a time. ADO.NET internally calls the GetEnumerator method when executing the stored procedure with the TVP parameter, and it handles the transfer of data from the collection to the TVP automatically.

Q.12. State The Limitations of TVP?

Ans: TVPs have several limitations:

  • TVPs are read-only after being passed to a stored procedure or UDF.
  • The OUTPUT keyword cannot be used with TVPs.
  • TVPs cannot be updated or modified directly.
  • The schema of a TVP cannot be altered using ALTER TABLE...AS TYPE; instead, you need to recreate it and any dependent objects.
  • Only PRIMARY KEY and UNIQUE constraints are supported for indexing in TVPs.
  • TVPs do not have statistics tracked by SQL Server.
  • TVPs are not supported by Entity Framework.

Conclusion

Table-Valued Parameters (TVPs) are a powerful feature in SQL Server that allow you to transfer sets of rows as parameters to stored procedures and UDFs. They offer several benefits, including reduced roundtrips and improved performance for bulk data operations. However, they have certain limitations that need to be considered while using them in your applications.

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