Sql query for updating database if value is not null?

Question

I am having a table which has about 17 fields. I need to perform frequent updates in this table. But the issue is each time I may be updating only a few fields.

Answer 1

Posting a SQL Server solution with 2 tables for posterity. Query joins two tables and updates the values that are present. Otherwise original value is maintained.

tables = table1, table2 each having field1 and field2

update t1 WITH (ROWLOCK)
set T1.Field2 = ISNULL(T2.Field2,T1.Field2)
from Table1 T1 Join Table2 T2 
    ON T1.Field1 = T2.Field1