I have a table (Table1) with the columns `order_item_id` `customer_id` and `order_id` in which I want to count the number of orders per customer. Unfortunately an order with more than one article has the same `order_id`

```
|order_item_id|order_id|customer_id|
|     2       |   30   |    1      | 
|     3       |   30   |    1      | 
|     4       |   42   |    1      | 
|     5       |   33   |    2      | 
|     11      |   32   |    3      | 
|     12      |   33   |    2      | 
|     13      |   33   |    2      | 
|     19      |   69   |    3      | 

```

Expected Outcome:

```
|numberOfOrders|customer_id|
|     2        |    1      | 
|     1        |    2      | 
|     2        |    3      | 

```

I tried this (and many more): 

```
CREATE TABLE X AS
   SELECT 
       customer_id, 
       COUNT(order_id) AS `numberOfOrders`
   FROM Table1 T1 
   GROUP BY customer_id;

```

The problem is, that with this solution it counts every article not the number of orders: so the number of orders for customer 1 is 3 (not 2), for customer 2 is 3 (not 1)....

How can I solve this for a big database with Mysql query?