Question

I have looked at
SQL update query using joins
..but it is not exactly what I need (I am used to cook-book SQL, and can’t figure out how to modify the answers).

I have a table “a” and a table “b”. I want to update field f1 in “a” if and only if “b” has a record with fields f1, f2, f3 equal to f1, f2, f3 in table “a”.

So, if I have

TABLE a
f1            f2            f3         ...
------------------------------------------
m             a1a 1a1       1-1-1980
m             a1a 1a1       1-1-1980
m             b1b 1b1       18-1-1982
m             c1c 1c1       16-4-1975

TABLE b
f1            f2            f3         ...
------------------------------------------
m             b1b 1b1       18-1-1982
m             c1c 1c1       16-4-1975

Do update. Then Table “a” looks like:

TABLE a
f1            f2            f3         ...
------------------------------------------
m             a1a 1a1       1-1-1980
m             a1a 1a1       1-1-1980
m             b1b 1b1       *-1-1982
m             c1c 1c1       *-4-1975

I know how to do the string manipulation… but the update query is not something I’m used to, especially in this context. I would appreciate your help.

Thank you!

EDIT: I am using sqlite

EDIT 2: Here is a query that user suggested, but it is not working currently to update records (probably my mistake):

UPDATE diseases
SET dateofbirth='*'||ltrim(dateofbirth,0123456789)
WHERE gender=(SELECT a1.gender FROM diseases AS a1 
              INNER JOIN stage2helper AS b ON     a1.gender = b.gender AND 
a1.dateofbirth = b.dateofbirth AND a1.postalcode = b.postalcode) 

AND postalcode=(SELECT a1.postalcode FROM diseases AS a1 INNER JOIN stage2helper AS b   ON a1.gender = b.gender AND a1.dateofbirth = b.dateofbirth AND a1.postalcode = b.postalcode) 

AND dateofbirth=(SELECT a1.dateofbirth FROM diseases AS a1 INNER JOIN stage2helper AS     b ON a1.gender = b.gender AND a1.dateofbirth = b.dateofbirth AND a1.postalcode =     b.postalcode);

Answer 1

In Transact-SQL you can do this

UPDATE a
SET    a.f3=yourfunctiontogeneratetext()
FROM   b
WHERE  a.f1=b.f1 AND a.f2=b.f2 AND a.f3=b.f3

Ok with ANSI SQL you can’t use the from syntax so try

UPDATE a
SET    a.f3=yourfunctiontogeneratetext()
WHERE  a.f1 = (SELECT a1.f1
               FROM a as a1
                    iNNER JOIN
                    b ON  a.f1=b.f1 AND a.f2=b.f2 AND a.f3=b.f3) and
       a.f2 = (SELECT a1.f2
               FROM a as a1
                    iNNER JOIN
                    b ON  a.f1=b.f1 AND a.f2=b.f2 AND a.f3=b.f3) and
       a.f3 = (SELECT a1.f3
               FROM a as a1
                    iNNER JOIN
                    b ON  a.f1=b.f1 AND a.f2=b.f2 AND a.f3=b.f3)

I did this on a tablet so please forgive any typos