SQL从多个表插入行

Question

I have got an assignment. We have been given a table, MAIN_TABLE, which has a column patient_id as foreign key.

I need to make a separate table named patient which has patient_id as a primary key along with some other attributes such as name and address.

I did successfully create schema of this table. Now there is a serious problem I am facing. After creating this table I used insert statement to insert values for name and address from a dummy table.

Till this point everything works fine. However, the column patient_id is still empty rather I have set it to 0 by default.

Now the problem is that I need to get values into this column, patient_id, from the patient_id column of MAIN TABLE.

I can't figure out how do I do this? I did try to use:

UPDATE patient
SET patient_id=(select id from MAIN_TABLE) 

BUT this gives me error that multiple rows returned which does make sense but what condition do I put in where clause then?

Answer 1

That sounds strange. How can there be a table MAIN_TABLE with a foreign key patient_id but the master table patient does not exist. Where do that patient_id s in MAIN_TABLE come from?

I suggest not to insert your data from a dummy table alone and then try to update it. But insert it with both - the MAIN_TABLE and the dummy table joined. If you can not join them. You would also not be able during the update.

So since i think they have no connected primary/foreign keys the only way to join them is using a good business key. Do you have a good business key? You are talking about persons. So First Name, Last Name, Birth Day, Address often is good enough. But you have to think about it.

With your given data I can only give you some kind of meta insert statement. But you will get the point.

Example:

insert into patient (col1, col2, col3)
select 
  a.colA, 
  a.colF,
  b.colX
from 
  dummy_table a
    inner join MAIN_TABLE b on a.colN=b.colA and a.colM=b.colB

And : If patient_id is your primary key in patient you should ensure that it is even not possible to have duplicate values or null in this column. And you should use constraints to ensure your data integrity.

http://docs.oracle.com/cd/B19306_01/server.102/b14200/clauses002.htm