1. UNION The UNION command is used to select related information from two tables,
much like the JOIN command. However, when using the UNION command all
selected columns need to be of the same data type. With UNION, only distinct values
2. UNION ALL The UNION ALL command is equal to the UNION command, except that
UNION ALL selects all values.
The difference between Union and Union all is that Union all will not eliminate duplicate
rows, instead it just pulls all rows from all tables fitting your query specifics and combines
them into a table.