Inserting into table from another table with an extra variable - sql

Question

I have two tables
Table A
(
unique id, -- sum of the records
Data1,
Data2
)
Table B
(
Data1,
Data2
)
I need to insert from table B into table A and add the records in. I had a simple insert like this:
Insert into A select * from B
but that does not work due to the unique ID.
I tried something like:
INSERT INTO A
SELECT 1+SELECT MAX(UniqueID) FROM A,temp.*
FROM B temp;
But this does not work. Can anyone think of a way I can get the first parameter to be a count of the records, obviously it would need to increase by one each time a new record is added.

Answer 1

Just set id to be an auto-increment column in the table declaration:
create table A (
id int primary key auto_increment,
Data1 <sometype>,
Data2 <sometype>
);
Then you can insert rows from B:
insert into A (Data1, Data2)
select Data1, Data2 from B
Each new row in A will get a new, unique auto-increment value for id.
Note: not experienced with plsql, but this is what I'd do with MySQL.

Answer 2

In past Oracle DB's, I've used a sequence to create a primary key ID for Table A, so you should be able to do this:
CREATE SEQUENCE A_SEQ
MINVALUE 1
MAXVALUE 999999999999999999999999999
START WITH 1
INCREMENT BY 1
CACHE 20;
insert into A (id, Data1, Data2) select A_SEQ.nextval, Data1, Data2 from B
See this url for details: http://www.techonthenet.com/oracle/sequences.php
** In SQL Server, you can use the "autoincrement" attribute on a column to do the same.
** SQL Server 2012 will also be gaining a similar Sequence mechanism, though its syntax is quite different than this.
** Edit: My preference is still to use sequences, but as an alternative, this re-work of your original SELECT statement might be helpful:
INSERT INTO A (UniqueID, Data1, Data2)
SELECT
(SELECT MAX(UniqueID) + 1 FROM A)
, Data1
, Data2
FROM B