SQL update query from existing table where 2 or more conditions exist

HI, everyone i'm new to the forum and have a problem ive been struggling with for a few days, am really hoping someone can help me:

Basically im looking to update a table from an exisitng table where 2 or more condtions exists in both tables

Will give my example in the hope anyway:

Table 1
id      PID      Sub            udf3
4      8      MAT             C
4      8      ENG      A
4      17      MAT        B
3      8      MAT            A
3      8      ENG       A
3       17      ENG       B

Table 2
ID5      PID      Sub            dtxt
23      8      MAT            null
23      8      ENG      null
24      8      ENG      null
24      17      MAT            null
23      17      FRE            null

Now, what i trying to do is update table2 (only records with id5 = '23'  with the values from table1 where  id = '4' and PID and Sub match those from table 2

All other entries to be left as null

Resulting in a table that looks like this:

Table 2
ID5      PID      Sub            dtxt
23      8      MAT            C
23      8      ENG      A
24      8      ENG      null
24      17      MAT            null
23      17      MAT            B            


I have tried an update query along the lines of:

SELECT pid, sub, grade FROM table1 where id = '4'

UPDATE table2 SET pid=table1.pid where id5 = '23'
UPDATE table2 SET sub=table1.sub where id5 = '23'
UPDATE table2 SET dtxt=table1.udf3 where id5 = '23'

Have also tried:

update table2
set dtxt = (select ud3 from table1 where table1.pid = pupilid and table1.sub = sub and table1.id =4 and pcheckid =23)
where exists
(select ud3 from report where table1.pid = pupilid and table1.sub = sub and table1.id =4 and pcheckid =23)

which returns more than one value and therfore fails

But so far no joy, any suggestions greatfully appreciated as ive been grappling with this for 3 days now.

Thanks in advance to everyone