MySQL Create entry for each row in a table - mysql

Question

I know there must be an answer to this, but I can't seem to put the search terms together properly.
Say I have an existing table 'foo'
foo
| id | data1 | data2 | ... |
----------------------------
|1 | abc | def | ghi |
|2 | abc | def | ghi |
...
And I want to create a new table, bar that has a 1 to 1 relationship with foo where foo gets a new foreign key column called barId, and each entry of foo MUST have a related barID so the end result looks like:
foo
| id | data1 | data2 | ... | barID |
------------------------------------
|1 | abc | def | ghi | 1 |
|2 | abc | def | ghi | 2 |
...
bar
| id | dataA | dataB |
----------------------
| 1. | null | null |
| 2. | null | null |
The trouble I'm having is that after I define bar I am having trouble creating a row for each entry of foo, and subsequently setting foo.barId for each newly created bar record.
If I were to do this in a procedural language, I would write something like the pseudocode below
createTable(bar);
foo.createColumn("barId");
for each (entry in foo) {
barEntry = bar.createNewEntry();
entry.setBarId(barEntry.ID);
}
How can I accomplish this goal with MySQL?

Answer 1

What part(s) of the problem does the following fail to address?
DROP TABLE IF EXISTS users;
CREATE TABLE users
(user_id SERIAL PRIMARY KEY
,user_name VARCHAR(12) UNIQUE
);
DROP TABLE IF EXISTS user_role;
CREATE TABLE user_role
(user_id INT NOT NULL PRIMARY KEY
,role ENUM('guest','user','administrator')
);
INSERT INTO users VALUES (NULL,'John');
INSERT INTO user_role VALUES (LAST_INSERT_ID(),'administrator');
SELECT * FROM users;
+---------+-----------+
| user_id | user_name |
+---------+-----------+
| 1 | John |
+---------+-----------+
1 row in set (0.00 sec)
SELECT * FROM user_role;
+---------+---------------+
| user_id | role |
+---------+---------------+
| 1 | administrator |
+---------+---------------+
EDIT: And extending this idea, consider the following...
INSERT INTO users (user_name) VALUES ('Paul'),('George'),('Ringo');
INSERT IGNORE INTO user_role SELECT user_id, 'guest' FROM users;
SELECT * FROM users;
+---------+-----------+
| user_id | user_name |
+---------+-----------+
| 1 | John |
| 2 | Paul |
| 3 | George |
| 4 | Ringo |
+---------+-----------+
SELECT * FROM user_role;
+---------+---------------+
| user_id | role |
+---------+---------------+
| 1 | administrator |
| 2 | guest |
| 3 | guest |
| 4 | guest |
+---------+---------------+
Note that it's slightly unusual to store 1-1 relations in separate tables, but there can be valid reasons for doing so - particularly relating to permissions.