Merge SQL Result Sets: UNION ALL vs JOIN

In SQL, the UNION ALL operator can be used to combine multiple result sets into one result set. For example:

SELECT column1 FROM table1
UNION ALL
SELECT column2 FROM table2

This will merge column1 from table1 and column2 from table2 into one result set. You can also connect multiple tables using JOIN operators and merge the result sets into one row. For example:

SELECT table1.column1, table2.column2 
FROM table1
JOIN table2 ON table1.id = table2.id

This will join the rows that meet the criteria in table1 and table2 together, merging them into one result set.