How can I run this SQL Server code in POSTGRESQL?

Question

Code in SQL Server:

SELECT
    a.ParcelID, a.PropertyAddress, 
    b.ParcelID, b.PropertyAddress,     
    ISNULL(a.PropertyAddress,b.PropertyAddress)
FROM
    PortfolioProject.dbo.NashvilleHousing a
JOIN 
    PortfolioProject.dbo.NashvilleHousing b ON a.ParcelID = b.ParcelID
                                            AND a.[UniqueID ] <> b.[UniqueID ]
WHERE
    a.PropertyAddress IS NULL

UPDATE a
SET PropertyAddress = ISNULL(a.PropertyAddress, b.PropertyAddress)
FROM PortfolioProject.dbo.NashvilleHousing a
JOIN PortfolioProject.dbo.NashvilleHousing b ON a.ParcelID = b.ParcelID
                                             AND a.[UniqueID ] <> b.[UniqueID ]
WHERE a.PropertyAddress IS NULL

Now, in PostgreSQL, I run the query like this:

SELECT 
  a.parcel_id, a.property_address, b.parcel_id, b.property_address, COALESCE(a.property_address, NULL, b.property_address, NULL) 
  FROM nashville_housing a
  JOIN nashville_housing b
    ON a.parcel_id = b.parcel_id
    AND a.unique_id <> b.unique_id
WHERE a.property_address IS NULL

The code above works, and shows me the rows of property_address that are null, and makes a new column COALESCE with the rows that I want to migrate to the column property_address .

UPDATE nashville_housing
SET property_address = COALESCE(a.property_address, NULL, b.property_address, NULL) 
FROM nashville_housing a
JOIN nashville_housing b
  on a.parcel_id = b.parcel_id
  AND a.unique_id <> b.unique_id
WHERE a.property_address IS NULL

Now, when I run this code, updates all the rows of the column property_address with the first match of COALESCE . I think is because I running COALESCE . When I check the function says: "The COALESCE function accepts an unlimited number of arguments. It returns the first argument that is not null. If all arguments are null, the COALESCE function will return null."

Answer 1

    SELECT 
      a.parcel_id, a.property_address, b.parcel_id, b.property_address, COALESCE(a.property_address, b.property_address)
      FROM nashville_housing a
      JOIN nashville_housing b
        ON a.parcel_id = b.parcel_id
        AND a.unique_id <> b.unique_id
    WHERE a.property_address IS NULL

UPDATE nashville_housing
SET property_address = COALESCE(nashville_housing.property_address, b.property_address)
FROM nashville_housing as b
WHERE nashville_housing.property_address IS NULL
AND nashville_housing.parcel_id = b.parcel_id
AND nashville_housing.unique_id <> b.unique_id