How to combine two tables containing both shared and distinct columns using data intervals in SQL?

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To combine two tables containing both shared and distinct columns using data intervals in SQL, you can use the JOIN clause with the ON condition specifying the data interval.

For example, suppose you have two tables named sales and expenses as follows:

sales table: sale_id | date | amount 1 | 2021-01-01 | 1000 2 | 2021-02-10 | 1500 3 | 2021-03-15 | 2000

expenses table: expense_id | date | amount 1 | 2021-01-05 | 500 2 | 2021-02-15 | 800 3 | 2021-03-20 | 1200 4 | 2021-04-01 | 1000

To combine these two tables based on the data interval of the month, you can use the following SQL statement:

SELECT s.saleid, s.date, s.amount, e.expenseid, e.amount FROM sales s LEFT JOIN expenses e ON DATEFORMAT(s.date, '%Y-%m') = DATEFORMAT(e.date, '%Y-%m');

This SQL query returns a new table with shared columns (saleid, date, and amount) and the distinct column (expenseid) from the expenses table, joined based on the data interval of the month.

The resulting table would look like this:

saleid | date | amount | expenseid | amount 1 | 2021-01-01 | 1000 | 1 | 500 2 | 2021-02-10 | 1500 | 2 | 800 3 | 2021-03-15 | 2000 | 3 | 1200 NULL | NULL | NULL | 4 | 1000

Note that the LEFT JOIN keyword is used to ensure that all rows from the sales table are included in the resulting table, even if there is no match in the expenses table for a given month.