How to update a single parent table based on multiple values in the child table

Question

I'm trying to update my parent table column if my child table column has all the same values for a single ParentId.

T1 - Parent

|      ParentId       |    StatusId      |
|---------------------|------------------|
|          1          |       1          |
|---------------------|------------------|
|          2          |       1          |
|---------------------|------------------|

T2 - Child

|      ChildId        |     ParentId     |    StatusId      |
|---------------------|------------------|------------------|
|          1          |       1          |        0         |
|---------------------|------------------|------------------|
|          2          |       1          |        0         |
|---------------------|------------------|------------------|
|          3          |       1          |        0         |
|---------------------|------------------|------------------| 
|          4          |       2          |        1         |
|---------------------|------------------|------------------| 
|          5          |       2          |        0         |
|---------------------|------------------|------------------| 

If T2 status column has all 0's for ParentId 1 then set status in T1 to 0 else if there is a 1 status for any ParentId in T2 then set the status in T1 to 1 or do nothing.

Desired Result after update statement:

T1 - Parent

|      ParentId       |    StatusId      |
|---------------------|------------------|
|          1          |       0          |
|---------------------|------------------|
|          2          |       1          |
|---------------------|------------------|

T2 - Child

|      ChildId        |     ParentId     |    StatusId      |
|---------------------|------------------|------------------|
|          1          |       1          |        0         |
|---------------------|------------------|------------------|
|          2          |       1          |        0         |
|---------------------|------------------|------------------|
|          3          |       1          |        0         |
|---------------------|------------------|------------------| 
|          4          |       2          |        1         |
|---------------------|------------------|------------------| 
|          5          |       2          |        0         |
|---------------------|------------------|------------------| 

I know can perhaps do something like this using an update and maybe a while loop but I'm not quite sure how to construct it. Any help is appreciated.

Answer 1

This can be done using an Update From Select

Update T1
    Set StatusID = newStatusID
From
(
    Select ParentID as changedParentID
        , max(StatusID) as newStatusID
    From T2
    Group By ParentID
)x
Where T1.ParentID = x.changedParentID
And T1.StatusID <> x.newStatusID