SQLite - Inserting values from multiple rows in the same table into a single row in another table - sqlite

Question

I have a table of phone numbers (tblPhoneNumbers):
ID, UserID, PhoneNumber
and I need to move them into a Users table (tblUsers) that contains:
ID, PhoneNumber1, PhoneNumber2
tblPhoneNumbers is assumed to have 2 rows for every user. Is it possible to move the PhoneNumber value of the first row into PhoneNumber1, and the PhoneNumber value of the second row into PhoneNumber2?
Essentially this is reverse-normalization but this is the task I need help with.
Thanks!
I need to use SQLite so I cannot use any syntax not available to SQLite.

Answer 1

If you're using sqlite 3.25 or better, you can use window functions to do it all in one statement (I assume here that the UserID column from tblPhoneNumbers is a foreign key that references ID from tblUsers, and that the given userid already has a record in that table; adjust as needed):
WITH allnumbers AS
(SELECT UserID
, PhoneNumber
, row_number() OVER (PARTITION BY UserID) AS num
FROM tblPhoneNumbers)
UPDATE tblUsers AS t
SET PhoneNumber1 = (SELECT a.PhoneNumber
FROM allnumbers AS a
WHERE a.UserID = t.ID AND num = 1)
, PhoneNumber2 = (SELECT a.PhoneNumber
FROM allnumbers AS a
WHERE a.UserID = t.ID AND num = 2);
(And if your system only has an older version that don't support window functions, you can always download a copy of the latest version of the sqlite3 shell and use it instead of the OS provided one).
(edit: You'll want an index on tblPhoneNumbers.UserID for better performance)

Answer 2

You could use the following :-
-- Create a temporary swap table
CREATE TEMP TABLE IF NOT EXISTS swapPhoneNumbers (ID INTEGER PRIMARY KEY, UserID INTEGER, PhoneNumber TEXT, replacementPhoneNumber TEXT);
-- Clear the temporary swap table in case it's used more than once
DELETE FROM swapPhoneNumbers;
-- Populate the temporary swap table according to the original data
INSERT INTO swapPhoneNumbers (ID,UserID,PhoneNumber) SELECT * FROM tblPhoneNumbers;
-- Update the swap table to include the replacement phone numbers
UPDATE swapPhoneNumbers SET replacementPhoneNumber = (
SELECT PhoneNumber FROM tblPhoneNumbers
WHERE swapPhoneNumbers.userID = tblPhoneNumbers.userID
AND swapPhoneNumbers.ID <> tblPhoneNumbers.ID
);
-- Update the original table with the new phone numbers
UPDATE tblPhoneNumbers SET PhoneNumber = (
SELECT replacementPhoneNumber FROM swapPhoneNumbers
WHERE tblPhoneNumbers.ID = swapPhoneNumbers.ID
);
The following is the SQL used to test the above.
-- Create Testing Table with some data
DROP TABLE IF EXISTS tblphoneNumbers;
CREATE TABLE IF NOT EXISTS tblPhoneNumbers (ID INTEGER PRIMARY KEY, userID INTEGER, PhoneNumber TEXT);
INSERT INTO tblPhoneNumbers (userID, PhoneNumber) VALUES
(1,'0111111111'),(1,'0222222222'),(2,'0333333333'),(2,'0444444444'),(3,'0555555555'),(3,'0666666666')
;
-- Show what is in the original table
SELECT * FROM tblPhoneNumbers;
-- Create a temporary swap table
CREATE TEMP TABLE IF NOT EXISTS swapPhoneNumbers (ID INTEGER PRIMARY KEY, UserID INTEGER, PhoneNumber TEXT, replacementPhoneNumber TEXT);
-- Clear the temporary swap table in case it's used more than once
DELETE FROM swapPhoneNumbers;
-- Populate the temporary swap table according to the original data
INSERT INTO swapPhoneNumbers (ID,UserID,PhoneNumber) SELECT * FROM tblPhoneNumbers;
-- Show what is in the swap table
SELECT * FROM swapPhoneNumbers;
-- Update the swap table to include the replacement phone numbers
UPDATE swapPhoneNumbers SET replacementPhoneNumber = (
SELECT PhoneNumber FROM tblPhoneNumbers
WHERE swapPhoneNumbers.userID = tblPhoneNumbers.userID
AND swapPhoneNumbers.ID <> tblPhoneNumbers.ID
);
-- Show what is now in the swap table
SELECT * FROM swapPhoneNumbers;
-- Update the original table with the new phone numbers
UPDATE tblPhoneNumbers SET PhoneNumber = (
SELECT replacementPhoneNumber FROM swapPhoneNumbers
WHERE tblPhoneNumbers.ID = swapPhoneNumbers.ID
);
-- Show what is in the original table
SELECT * FROM tblPhoneNumbers;
And this is some screen shots from doing it