如何检查两个不同表中两列数据的存在？ 的MySQL

Question

I have two different tables in two different databases ..

what I want to do is to check if the data of two columns exist in the other table .. if it does exist count it and at the final I want the number of records that have matching in the other table.

example :

table_1

column_1 value = "dog"

column_2 value = "apple"

table_2

column_1 value = "dog"

column_2 value = "orange"

so here the first column values exist in both table but the second column is different so I don't want to count it .. I want to count where both values exist in the same record .

ps: Both column_1 and column_2 aren't primary key

is there a solution for it using MySQL ? because I used java to solve this but take a long time for 5 million records .

Answer 1

Do an INNER JOIN on both tables:

SELECT COUNT(*)
FROM table_1 t1
INNER JOIN table_2 t2
    ON t1.column_1 = t2.column_1
    AND t1.column_2 = t2.column_2

Answer 2

If I'm understanding you correctly, one option is to use exists :

select * 
from table1 t1
where exists (
    select 1
    from table2 t2 
    where t1.column1 = t2.column1 and
          t1.column2 = t2.column2
)

This will return a list of rows from the first table that have a corresponding matching row in the second.