How to search for NULL in Android database query &

a couple of queries regarding a database query:

So I have the following database query, which has a WHERE statement which includes three String variables (rackingSystem, manufacturer, "Amber Risk").

public Cursor fetchComponentsAndSpecForManufacturer(long inspectionId, String rackingSystem, String manufacturer) {
    Cursor mCursor =
            rmDb.query(true, DAMAGED_COMPONENTS_TABLE, new String[] {
                    DAMAGED_COMPONENT_ID,
                    LOCATION_LINK,
                    RUN_LINK,
                    AREA_LINK,
                    INSPECTION_LINK,
                    LOCATION_REF,
                    RACKING_SYSTEM,
                    COMPONENT,
                    COMPONENT_TYPE,
                    QUANTITY,
                    POSITION,
                    RISK,
                    ACTION_REQUIRED,
                    NOTES_GENERAL,
                    MANUFACTURER,
                    TEXT1,
                    TEXT2,
                    TEXT3,
                    TEXT4,
                    NOTES_SPEC,
                    SPEC_SAVED}, 
                    INSPECTION_LINK + " = " + inspectionId + " AND " + RACKING_SYSTEM + " = ? AND " + MANUFACTURER + " = ? AND " + RISK + " = ? ", 
                    new String[] {rackingSystem, manufacturer, "Amber Risk"},
                    COMPONENT_TYPE + ", " + TEXT1 + ", " + TEXT2 + ", " + TEXT3 + ", " + TEXT4 + ", " + NOTES_SPEC,
                    null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

Question 1:

How do I search for NULL as, in the above example, manufacturer may be NULL in the database (as the user may not have inputed anything into the database for that bit yet).

Question 2:

Can I include an OR statement in the WHERE statement? So at the moment I am seraching for all records that are "Amber Risk", but I need to also include in this list entries that are "Red Risk". If I can do this, how should I edit the WHERE statement?

How do I search for NULL as, in the above example, manufacturer may be NULL in the database

Use MANUFACTURER + " IS NULL".

Can I include an OR statement in the WHERE statement?

Yes. Let's search for null or empty manufacturers:

MANUFACTURER + " IS NULL OR " + MANUFACTURER + " = ''"

So at the moment I am seraching for all records that are "Amber Risk", but I need to also include in this list entries that are "Red Risk".

INSPECTION_LINK + " = " + inspectionId + " AND " + RACKING_SYSTEM + " = ? AND " + 
        MANUFACTURER + " IS NULL AND (" + RISK + " = ? OR " + RISK + " = ?)", 
new String[] {rackingSystem, manufacturer, "Amber Risk", "Red Risk"},