条件在2个表中，但仅从一个表中选择

Question

I have two tables in a mysql database.

I need to select columns just from the first table and do the condition in the 2 table for example :

I have in the first table the columns:

amount | date | name | address

and in the second I have:

amount | date | cin | time 

The condition would be WHERE amount = amount and date = date .

But select just the data from the first table. I dont need to display the data of the second table.

Answer 1

You could use the EXISTS operator to find out whether a corresponding row in the second table exists:

SELECT * FROM first_table t1
WHERE EXISTS (
    SELECT 1 
    FROM second_table t2
    WHERE
        t1.amount = t2.amount AND t1.date = t2.date
);

This ensures you won't have to use DISTINCT to reduce your resultset, if more than one row with your condition exists in the second table.