Compare table structure and add the missing columns

Question

Hello,
I want to compare the table schema of two tables and update with some plsql code the second one with the missing columns of the fist one :
Example
SQL> desc a
Name Type Nullable Default Comments
C1 VARCHAR2(10) Y
C2 NUMBER(3) Y
C3 NUMBER(10,2) Y
SQL> desc b
Name Type Nullable Default Comments
C1 VARCHAR2(10) Y
C2 NUMBER(3) Y
I want a script that will generate the following code
alter table b add (c3 number(10,2))
Thanks
Andreas

Answer 1

How abt the below mentioned code
SQL>desc a
Name Null? Type
C1 VARCHAR2(30)
C2 NUMBER(3)
C3 NUMBER(10,2)
C4 NOT NULL DATE
C5 VARCHAR2(30)
SQL>desc b
Name Null? Type
C1 VARCHAR2(30)
SQL>ed
Wrote file afiedt.buf
1 Declare
2 Cursor c1 is select Column_name,Data_length,Data_type,DATA_PRECISION,DATA_SCALE,
3 Nullable
4 From User_tab_columns
5 Where Table_name = 'A';
6 v_length Number;
7 v_str Varchar2(200);
8 v_null Varchar2(10);
9 Begin
10 For c2 in c1 loop
11 Select count(1) into v_length
12 From user_tab_columns
13 Where Table_name = 'B'
14 And Column_name = c2.column_name;
15 if v_length = 0 Then
16 Select Decode(c2.Nullable,'N','NOT NULL','') into v_null From Dual;
17 if c2.Data_type = 'NUMBER' Then
18 v_str := 'alter table b add '||c2.column_name||
19 ' '||c2.data_type||'('||c2.data_precision||','||c2.data_scale||') '||
20 v_null;
21 Elsif c2.Data_type = 'DATE' Then
22 v_str := 'alter table b add '||c2.column_name||
23 ' '||c2.data_type||' '||v_null;
24 Else
25 v_str := 'alter table b add '||c2.column_name||
26 ' '||c2.data_type||'('||c2.data_length||') '||v_null;
27 End if;
28 Execute immediate v_str;
29 End if;
30 End loop;
31* End;
SQL>/
PL/SQL procedure successfully completed.
Elapsed: 00:00:04.03
SQL>desc b
Name Null? Type
C1 VARCHAR2(30)
C2 NUMBER(3)
C3 NUMBER(10,2)
C4 NOT NULL DATE
C5 VARCHAR2(30)