I'm attempting to update a large product catalogue using a SQL query via phpMyAdmin if:

1. the _stock_status = onbackorder
2. the _stock > 0

Queries attempted:

Update wp_postmeta 
Set meta_value = 'instock' 
Where meta_key = '_stock' 
And meta_value > 0

Update wp_postmeta 
Set meta_value = 'instock' 
Where meta_value = 'onbackorder' 
And meta_key = '_stock_status'
And meta_value > 0
And meta_key = "_stock"

Update wp_postmeta 
Set meta_value = 'instock' 
Where meta_value = 'onbackorder' 
And '_stock' > 0

None of the above have worked.
The last query reduces all stock quantities to 0 but the stock status remains on "backorder"