Question

I have two tables I want to update table b in column bcnt by the value that in column acnt in table A where the worlds column in table A match words column in table B, and id in table B match id in table A.

create table a 
( 
    id number(9),
    words varchar2(2), 
    acnt number(9)
);

insert into a values(1,'Cairo',20);
insert into a values(1,'UK',10);
insert into a values(2,'KL',2);
insert into a values(2,'Cairo',2);
insert into a values(2,'London',30);
insert into a values(3,'Cairo',5);
insert into a values(4,'KSA',15);

create table b 
(
     id number(2), 
     words varchar2(20), 
     bcnt number
);

insert into b values(1,'Cairo',null);
insert into b values(1,'UK',null);
insert into b values(2,'KL',null);
insert into b  values(2,'Cairo',null);
insert into b values(3,'Cairo',null);
insert into b values(4,'KSA',null);

I used this SQL code but it is not correct.

update b 
set bcnt = (select acnt 
            from a 
            where a.id = b.id and a.words = b.words);

Expected results:

1   cairo  20
1   uk     10
2    kl     2
2   cairo   5 
4   ksa     12

The SQL shows me the following

SQL> /

        ID WORDS                      BCNT
---------- -------------------- ----------
         1 Cairo
         1 UK                           10
         2 KL                            2
         2 Cairo
         3 Cairo
         4 KSA

6 rows selected.

SQL>

Answer 1

Is the problem that your SQL uses word instead of words as in the table definition?

update b
    set bcnt=(select acnt from a where a.id=b.id and a.words=b.words );

Also, your data types are not correct in the two tables. Your create table statements should be consistent:

create table a (id number(9),words varchar2(20), acnt number);
create table b (id number(9), words varchar2(20), bcnt number);

What is happening is that the values longer than 2 characters in the first table are being truncated to two characters. So, instead of ‘Cairo’ the value is ‘Ca’ (to fit in varchar2(2)). As a result, you have no match in the join.