SQL dynamic column mapping between tables using reference table

Data and Databases
1

I’m working on a database issue where I need to move data from one table to another while using a mapping table. Here’s my setup:

Target Table (initially empty):

Employee Designation

Source Table (holds actual records):

ColumnA ColumnB
Ravi Developer
Swathi HR

Mapping Table (describes relationships between columns):

SourceColumn DestinationColumn
Employee ColumnA
Designation ColumnB

Desired Outcome for Target Table:

Employee Designation
Ravi Developer
Swathi HR

The difficulty I face is that I need to fill the Target Table with information from the Source Table, but the column names are different. I have to rely on the Mapping Table to understand the corresponding columns. Since the layout of the Source Table may vary often, I cannot hardcode the column names. The entire mapping process has to be completely dynamic as per the Mapping Table contents. How can I create an SQL query that achieves this dynamic column mapping and data insertion?

2

Interesting challenge! What happens when your source table has extra columns not in the mapping table? Does the mapping handle data type conversions or just column names? You’ll probably need error handling for when the mapping gets out of sync too.

3

Yeah, dynamic SQL is the way to go here. Query your mapping table first to figure out which columns match up, then build your INSERT statement from that. I usually write a stored procedure that reads the mapping table, creates a SELECT with the right column aliases, and runs the INSERT. You’d end up with something like INSERT INTO TargetTable (Employee, Designation) SELECT ColumnA AS Employee, ColumnB AS Designation FROM SourceTable. Just watch out for SQL injection when you’re building these statements dynamically. I’ve used this approach in production before - performance isn’t an issue since the mapping only runs once per data load.

4

that sounds tricky! u gotta use dynamic sql to get the column names from your mapping table. then, construct your insert stmt dynamically. just keep an eye on any quirks specific to your db engine. you got this!