How do you select distinct multiple columns in PostgreSQL?

 In PostgreSQL, to select distinct combinations of multiple columns, you can use the DISTINCT keyword followed by the column names separated by commas. Here's the general syntax:

SELECT DISTINCT column1, column2, column3
FROM table_name;

This query will return only unique combinations of values from the specified columns (column1, column2, column3, etc.) in the table_name.

Example:

Suppose you have a sales table with the columns product_id, store_id, and sale_date, and you want to get all distinct combinations of product_id and store_id:

SELECT DISTINCT product_id, store_id
FROM sales;

This will return all unique pairs of product_id and store_id from the sales table, eliminating any duplicates.

Notes:

• If any of the columns have NULL values, these will also be treated as distinct, even though they represent missing data.
• You can add more columns to the list to get distinct combinations across multiple fields.