Code Generator | SQL

join_fact_tables

A function that joins two fact tables using a common key column

Prompt

Answer

-- Function: join_fact_tables

-- Purpose: Join two fact tables using a common key column

-- Parameters:
--   @fact_table1: Name of the first fact table
--   @fact_table2: Name of the second fact table
--   @key_column: Common key column to join the tables on

-- Returns: Joined fact table

CREATE OR REPLACE FUNCTION join_fact_tables (
    @fact_table1 varchar(255),
    @fact_table2 varchar(255),
    @key_column varchar(255)
)
RETURNS TABLE (
    joined_fact_table fact_table_type
)
AS $$
BEGIN
    -- Create a dynamic query to join the fact tables
    EXECUTE FORMAT('SELECT * FROM %I JOIN %I ON %I.%I = %I.%I', @fact_table1, @fact_table2,
                   @fact_table1, @key_column, @fact_table2, @key_column)
    INTO joined_fact_table;
    
    RETURN;
END;
$$ LANGUAGE plpgsql;

Description

This SQL function called join_fact_tables is designed to join two fact tables using a common key column. The function takes three parameters: fact_table1 which is the name of the first fact table, fact_table2 which is the name of the second fact table, and key_column which is the common key column to join the tables on.

The function returns a joined fact table, represented as joined_fact_table. It creates a dynamic query using the EXECUTE FORMAT statement, where the names of the fact tables and the key column are inserted into the query string. The query performs an inner join on the two fact tables based on the common key column.

Once the join is executed, the result is stored into the joined_fact_table variable. Finally, the function returns the joined fact table.