Question

I have following table structure, with many tables like this:

data_1:
+-------+--------+-------+
| views | clicks | date  |
+-------+--------+-------+
|    29 |     1  | ..... |
|   458 |     9  | ..... |
+-------+--------+-------+ 
....

data_43:
+-------+--------+-------+
| views | clicks | date  |
+-------+--------+-------+
|     0 |     0  | ..... |
|     0 |     0  | ..... |
+-------+--------+-------+ 
...

My question here is, how can I get all the sum values in one query?

I tried it with a simple join:

mysql> SELECT SUM(t1.views)  data_1_views,
              SUM(t1.clicks) data_1_clicks,
              SUM(t2.views)  data_43_views,
              SUM(t2.clicks) data_43_clicks
       FROM data_1 t1, data_43 t2;

But my result isn’t what I expected:

+--------------+---------------+---------------+----------------+
| data_1_views | data_1_clicks | data_43_views | data_43_clicks |
+--------------+---------------+---------------+----------------+
|         NULL |          NULL |          NULL |           NULL |
+--------------+---------------+---------------+----------------+

I expected it to be:

+--------------+---------------+---------------+----------------+
| data_1_views | data_1_clicks | data_43_views | data_43_clicks |
+--------------+---------------+---------------+----------------+
|         487  |          10   |             0 |              0 |
+--------------+---------------+---------------+----------------+

Anyone here who can help me with this query?
I am also interested if this is more performant than doing all this stuff in multiple queries

Answer 1

In this case multiple queries are fine especially if you are grouping many rows. There is virtually no benefit (and actually potential bugs) lumping these two tables in one query.
I would just make two queries

SELECT SUM(t1.views) data_1_views, SUM(t1.clicks) data_1_clicks
FROM data_1 t1 

SELECT SUM(t2.views) data_43_views, SUM(t2.clicks) data_43_clicks
FROM data_43 t2;