使用合并函数更新 PostgreSQL 中的表

Question

I am exploring this house data and there are some rows where there are 2 same data with different unique id but only one's address is missing so i wrote this code but i do not know where i am making the mistake.

UPDATE A
SET PROPERTYADDRESS = COALESCE(A.PROPERTYADDRESS,B.PROPERTYADDRESS)
FROM "House" A
JOIN "House" B ON A.UNIQUEID != B.UNIQUEID
AND A.PARCELID = B.PARCELID
WHERE A.PROPERTYADDRESS IS NULL

When i run this code i am getting this error

ERROR:  relation "a" does not exist
LINE 1: UPDATE A

Answer 1

Postgres uses a different UPDATE syntax when you want to "join" some table than SQL Server for which your query is written (both are non-standard).

The target table should not be repeated in the FROM clause unless you want a self join. But then you should only put it into the FROM clause but not "join" it into the result a third time through a JOIN operator.

As you only select rows from the target table where propertyaddress is NULL, the coalesce is not necessary.

So you probably want:

UPDATE "House" A
  SET PROPERTYADDRESS = B.PROPERTYADDRESS
FROM "House" B 
WHERE A.UNIQUEID != B.UNIQUEID
  AND A.PARCELID = B.PARCELID
  AND A.PROPERTYADDRESS IS NULL