How to Efficiently Insert Data into Parent and Child Tables with Correct Mapping?

Insert data into the parent-child table

The goal of this example is to insert data from an incoming UDT (@tEmployeeData) into multiple tables, ensuring correct mapping between parent and child records.

Solving mapping issues

To establish the necessary mapping, we add a temporary employeeId column to the UDT and fill it with continuous values. Additionally, we create a table variable (@EmployeeidMap) to map the temporary employee ID in the UDT with the actual employee ID generated in the target table.

Populate the main table

We utilize MERGE to populate the @MainEmployee table with values ​​from the inserted data and source data. This allows us to capture the generated EmployeeID value and populate the mapping table at the same time.

<code class="language-sql">MERGE INTO @MainEmployee USING @tEmployeeData AS sourceData ON 1 = 0
WHEN NOT MATCHED THEN
INSERT (FirstName, LastName)
VALUES (sourceData.FirstName, sourceData.LastName)
OUTPUT sourceData.EmployeeId, inserted.EmployeeID 
INTO @EmployeeidMap (temp_id, id);</code>

Map and insert into parent-child tables

We then join @tEmployeeData with @EmployeeidMap to get the actual employee ID, which we use to populate the @ParentEmployeeDepartment table. Similarly, we connect @ParentEmployeeDepartment with @tEmployeeData to map parent ID to child data and insert the data into @ChildEmployeeDepartmentTypeA and @ChildEmployeeDepartmentTypeB.

Test insert

To verify that the mapping was successful, we execute a query that joins the UDT data with the mapping and target tables.

<code class="language-sql">SELECT FirstName,
     LastName,
     SentData.DepartmentType As [部门类型],
     DepartmentBuilding As 建筑物,
     DepartmentEmployeeLevel As [员工级别],
     DepartmentTypeAMetadata As [A 元数据],
     DepartmentTypeBMetadata As [B 元数据],
     SentData.EmployeeId As 临时ID, EmpMap.id As [员工ID], DeptMap.ParentEmployeeDepartmentID As [部门ID]
FROM @tEmployeeData SentData
INNER JOIN @EmployeeidMap EmpMap ON SentData.EmployeeId = temp_id 
INNER JOIN @ParentEmployeeDepartment DeptMap ON EmpMap.id = DeptMap.EmployeeID</code>

This approach ensures that child data is correctly mapped to its respective parent record, while optimizing performance by avoiding unnecessary row-by-row operations.

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