Postgresql 将列从一个表更新到另一个表

Question

How do i update inventory_id in TABLE2 from TABLE1 inventory_id?

So far I've tried

UPDATE TABLE2
SET 
inventory_id=t1.inventory_id
FROM TABLE2 t2
INNER JOIN
TABLE1 t1
ON t1.test_id = t2.test_id
WHERE t1.test_id = t2.test_id;

But this sets all the value of inventory_id in TABLE2 as 1 instead of my expected result.

TABLE1
inventory_id     test_id
1                         26
2                         56
3                         12
4                         67

TABLE2
test_id       inventory_id
12
26
56
67

Such that it becomes like this?

TABLE2
test_id       inventory_id
12              3
26              1
56              2
67              4

Answer 1

The documentation on UPDATE states:

 UPDATE [ ONLY ] table_name [ * ] [ [ AS ] alias ]... [ FROM from_item [, ...] ]

(...)

from_item

A table expression allowing columns from other tables to appear in the WHERE condition and update expressions. This uses the same syntax as the FROM clause of a SELECT statement; for example, an alias for the table name can be specified. Do not repeat the target table as a from_item unless you intend a self-join (in which case it must appear with an alias in the from_item ).

(emphasis: me)

So following that you want:

UPDATE table2 t2
       SET inventory_id = t1.inventory_id
       FROM table1 t1
            WHERE t1.test_id = t2.test_id;

db<>fiddle

You pretty much had it but seem to got confused by the syntax you may have seen for other DBMS and mixed them.

Answer 2

Normally the PostgreSQL UPDATE JOIN syntax should give:

UPDATE TABLE2 t2
SET 
t2.inventory_id=t1.inventory_id
FROM TABLE1 t1
WHERE t1.test_id = t2.test_id;