SQL left join but only take the specific condition on a column

I have two tables, the first is a table that contains status and the second is contains balance. I want to join those two tables but with only specific status on the first table

Sample Data Table 1

+------------------+------------------+--------------+
|   appsflyer_id   |   customer_id    |    status    |
+------------------+------------------+--------------+
|       AA1        |        123       |     NEW      |
|       AA1        |        123       |    ACTIVE    |
|       AA1        |        124       |     NEW      |
|       AA1        |        124       |    ACTIVE    |
+------------------+------------------+--------------+

Sample Data Table 2

+------------------+--------------+
|   customer_id    |   balance    |
+------------------+--------------+
|        123       |     100      |
|        124       |     250      |
+------------------+--------------+

Desired output

+------------------+------------------+--------------+------------------+
|   appsflyer_id   |   customer_id    |    status    |     balance      |
+------------------+------------------+--------------+------------------+
|       AA1        |        123       |     NEW      | (null/zero/empty)|
|       AA1        |        123       |    ACTIVE    |     100          |
|       AA1        |        124       |     NEW      | (null/zero/empty)|
|       AA1        |        124       |    ACTIVE    |     250          |
+------------------+------------------+--------------+------------------+

I tried to use:

SELECT appsflyer_id, a.customer_id, status, balance
FROM `table_1` a left join `table_2` b on a.customer_id = b.customer_id

It will return multiple balance which is not quite right

+------------------+------------------+--------------+------------------+
|   appsflyer_id   |   customer_id    |    status    |     balance      |
+------------------+------------------+--------------+------------------+
|       AA1        |        123       |     NEW      |     100          |
|       AA1        |        123       |    ACTIVE    |     100          |
|       AA1        |        124       |     NEW      |     250          |
|       AA1        |        124       |    ACTIVE    |     250          |
+------------------+------------------+--------------+------------------+

Answer

Looks like you want CASE

SELECT a.appsflyer_id, a.customer_id, a.status, 
      CASE WHEN a.status = 'ACTIVE' THEN b.balance END balance
FROM `table_1` a 
LEFT JOIN `table_2` b on a.customer_id = b.customer_id