How to Efficiently Merge Multiple DataTables with Different Column Sets?

Combining Multiple DataTables into a Single DataTable with Different Column Sets

A common scenario in data processing involves combining multiple tables into a single comprehensive one. While the tables may share some columns, their overall structures can vary. This question explores an efficient method to merge such tables, aligning their rows and filling missing values in a user-friendly manner.

The Challenge

The provided code employs a loop to iteratively retrieve data from individual tables and merge them into a single DataTable. However, this basic approach results in misaligned data, with blank cells appearing in the merged table. The goal is to find an improved way to merge these tables, ensuring proper row alignment and seamless data integration.

Solution Using the MergeAll Method

To address the misalignment issue, the provided code includes a custom MergeAll extension method for IList specifically designed for this task. It takes an optional primary key column name as an argument and ensures that merging maintains row alignment.

Here's how the MergeAll method operates:

• Input Validation: It verifies that the input list of DataTables is not empty and, if a primary key column is specified, ensures that all tables contain that column.
• Table Handling: For cases with a single table, it returns the table directly. Otherwise, it initializes a new DataTable with the specified name.
• Data Loading: It optimizes data loading by disabling notifications, index maintenance, and constraints during the loading process.
• Merging: It iteratively merges each table into the consolidated table, effectively combining all their data.
• Row Alignment: If a primary key column was provided, it identifies and merges duplicate rows, filling missing values from other rows in the group.

Usage of MergeAll

To utilize the MergeAll method, simply provide a list of DataTables and specify the primary key column name (if applicable):

var tables = new[] { tblA, tblB, tblC };
DataTable tblUnion = tables.MergeAll("c1");

An Alternative Approach for Merging by Row Index

In situations where there's no direct column relationship between tables, but rows in both tables need to be aligned based on their index, the MergeTablesByIndex method can be used:

public static DataTable MergeTablesByIndex(DataTable t1, DataTable t2)
{
    // ... Implementation details here
}

This method clones the first table, adds missing columns from the second table with appropriate naming conventions, and merges row data based on the row index.

Conclusion

Utilizing these methods, you can effectively merge DataTables with varying column sets, ensuring proper row alignment and seamless data integration. The MergeAll method is particularly useful when row alignment is important, while the MergeTablesByIndex method is suitable for merging by row index.

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