How to Efficiently Insert Data into Parent and Child Tables Using a User-Defined Table Type in a Stored Procedure?

Efficiently Populating Parent and Child Tables within a Stored Procedure

This document outlines a solution for efficiently inserting data into parent and child tables within a stored procedure, leveraging a user-defined table type (UDT) for data input. The approach addresses the challenges of maintaining data integrity and avoiding performance bottlenecks associated with row-by-row operations.

The Challenge: Data Integrity and Performance

The challenge lies in accurately mapping data from a UDT to multiple related tables (a parent table and its associated child tables) within a stored procedure. Simple row-by-row inserts can be inefficient and prone to errors, especially when dealing with large datasets.

The Solution: A Multi-Step Approach

This solution employs a multi-step process to ensure both efficiency and data integrity:

1. Augmenting the UDT: Add a temporary ID column (temp_id) to the UDT. This serves as a unique identifier for each row within the UDT, crucial for tracking data across the insertion process.

2. Employing MERGE for Parent Table Insertion: The MERGE statement efficiently inserts data into the parent table (@MainEmployee). Critically, its OUTPUT clause captures both the temporary ID (temp_id from the UDT) and the newly generated EmployeeID from the parent table.

3. Creating a Mapping Table: The OUTPUT data from the MERGE statement populates a temporary mapping table (@EmployeeidMap). This table links the temporary temp_id to the actual EmployeeID generated in the parent table.

4. Parent Table Population with ID Mapping: The @EmployeeidMap table is then used to join the UDT data with the parent table (@ParentEmployeeDepartment), ensuring the correct EmployeeID is assigned to each parent record.

5. Child Table Population: Finally, the child tables (@ChildEmployeeDepartmentTypeA, @ChildEmployeeDepartmentTypeB) are populated using joins with both the @EmployeeidMap and @ParentEmployeeDepartment tables. This establishes the necessary relationships between parent and child records.

Illustrative Code Example:

The following code demonstrates this enhanced approach:

<code class="language-sql">CREATE TYPE dbo.tEmployeeData AS TABLE 
(
     FirstName NVARCHAR(50),
     LastName NVARCHAR(50),
     DepartmentType NVARCHAR(10),
     DepartmentBuilding NVARCHAR(50),
     DepartmentEmployeeLevel NVARCHAR(10),
     DepartmentTypeAMetadata NVARCHAR(100),
     DepartmentTypeBMetadata NVARCHAR(100),
     temp_id INT IDENTITY(1,1) -- Added temporary ID column
)
GO

CREATE PROC dbo.EmployeeImport 
    (@tEmployeeData dbo.tEmployeeData READONLY)
AS
BEGIN
    -- ... (Temporary table declarations remain the same as in the original example) ...

    -- MERGE into @MainEmployee table
    MERGE INTO @MainEmployee USING @tEmployeeData AS sourceData ON 1 = 0
    WHEN NOT MATCHED THEN
        INSERT (FirstName, LastName)
        VALUES (sourceData.FirstName, sourceData.LastName)
    OUTPUT sourceData.temp_id, inserted.EmployeeID 
    INTO @EmployeeidMap;

    -- ... (Remaining INSERT statements adjusted to use @EmployeeidMap for joining) ...
END
GO</code>

This refined strategy guarantees efficient and accurate data insertion, preserving referential integrity between parent and child tables while handling potentially large datasets effectively.

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