MySQL: choose Distinct from two different tables?

Question

I have two different tables, each of which has a column called product_type . How can I get the DISTINCT values ​​for product_type for both tables? Just to clarify if both tables have a diamond product_type, I want it to return once. Basically, it’s as if both tables where they were combined, and I selected a separate product_type from it.

Thanks!!

Answer 1

Use distinctive from a subquery that contains a union

select distinct product_type from ( select product_type from table 1 union select product_type from table 2 ) t 

Answer 2

Use different and combine:

 select distinct product_type from table1 union select distinct product_type from table2 

Merge removes duplicates when merging results.

Answer 3

Note that the UNION clause returns unique field values ​​when you want it to return ALL values ​​that you should use UNION ALL ...

 select product_type from table_a union product_type from table_b