Question

I have two tables table1, table2. Both the tables can be joined based on empID.

I have a new column in table1 called tabseqno. I want to update tabseqno of table1 with tabseqno from table2.

UPDATE TABLE1  SET TABLE1.TABSEQNO =TABLE2.TABSEQNO
WHERE TABLE1.EMPID= TABLE2.EMPID AND TABLE2.GROUPID=99

Answer 1

Either:

update table1 set table1.tabseqno =
  ( select table2.tabseqno from table2
    where table2.empid = table1.empid
    and table2.groupid = 99);

or:

update table1 set table1.tabseqno =
  ( select table2.tabseqno from table2
    where table2.empid = table1.empid
    and table2.groupid = 99)
where exists
  ( select table2.tabseqno from table2
    where table2.empid = table1.empid
    and table2.groupid = 99);

depending on what you want to happen if there is no matching table2 row for a table 1 row (the first statement will set table1.tabseqno to null, the second will not update those rows at all).

Both only work if the table2 subquery can only return a maximum of 1 row for any empid.