postgresqlHow do I use PostgreSQL's MERGE statement?

The PostgreSQL MERGE statement is a powerful way to combine data from multiple sources into a single table. It allows you to efficiently update, insert, and delete data in a table based on data from other tables.

Here is an example of how to use the MERGE statement:

MERGE INTO target_table USING source_table
ON (target_table.id = source_table.id)
WHEN MATCHED THEN
  UPDATE SET target_table.value = source_table.value
WHEN NOT MATCHED THEN
  INSERT (id, value) VALUES (source_table.id, source_table.value);

This example code will update the target_table with any matching rows from the source_table, and insert any new rows from the source_table into the target_table.

The code can be broken down into the following parts:

• MERGE INTO is used to specify the target table for the operation.
• USING is used to specify the source table for the operation.
• ON is used to specify the join condition between the target and source tables.
• WHEN MATCHED THEN is used to specify the action to take on rows that match the join condition.
• WHEN NOT MATCHED THEN is used to specify the action to take on rows that do not match the join condition.

For more information about the PostgreSQL MERGE statement, please see the following links:

• PostgreSQL Documentation: MERGE
• PostgreSQL Tutorial: MERGE

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