How to wite an update query with table joins?

Question

Table Name : Hist_table

 Shp_cd wt_grp  net_wt  tot_wt
   101   10       9      7
   102   20       8      2
   103   15       4      1

Factor_table

Fact_id fact_column factor
  1     wt_grp        2
  2     net_wt        5
  3     tot_wt        3

Note – this factor table contains rows as the column name of hist_table.
Now we have to update the Hist_table with the multiplied with the factors
For example wt_grp factor is 2 then we have to update all the wt_grp column of hist table as Hist_table.wt_grp * factor_table.factor
So the result should be

shpcd   wt_grp  net_wt  tot_wt
101     20        45    21
102     40        40    6
103     30        20    3

Answer 1

this is Postgres UPDATE JOIN format:

UPDATE address 
SET cid = customers.id
FROM customers 
WHERE customers.id = address.id

Here's the other variations: http://mssql-to-postgresql.blogspot.com/2007/12/updates-in-postgresql-ms-sql-mysql.html

Answer 2

UPDATE

table1
INNER

JOIN table2
ON

table1.field1 = table2.field2
SET

table1.field3 = table2.field4 WHERE ...... ;