SQL to normalize existing (many-to-many) data - sql

Question

Summary:
See below for Details. I'm copying the [unanswered] many-to-many question here to the top for readability:
Given the "Input" table, what is the SQL to generate the 3rd "Output"
table (Person_plays_Instrument)?
Current input (1 table):
OriginalTable:
PersonId PersonName Instrument_1 Instrument_2 Instrument_3 MailingAddress HomePhone
--------|----------|------------|------------|------------|--------------|------------
1 Bob Violin Viola Trumpet someplace 111-111-1111
2 Suzie Cello Flute <null> otherplace 222-222-2222
3 Jim Violin <null> <null> thirdplace 333-333-3333
Desired output (3 tables):
Person:
Id Name MailingAddress HomePhone
--|------|--------------|------------
1 Bob someplace 111-111-1111
2 Suzie otherplace 222-222-2222
3 Jim thirdplace 333-333-3333
Instrument:
Id Name
--|-------
1 Violin
2 Cello
3 Viola
4 Flute
5 Trumpet
Person_plays_Instrument:
PersonId InstrumentId
--------|------------
1 1
1 3
1 5
2 2
2 4
3 1
Details:
I have a single flat SQL table which started out as a spreadsheet. I'd like to normalize it. I'll split this into 1 question for each table.
Questions 1 and 2 have been answered, but I am leaving them in in case others find them helpful.
Questions:
Question #1: [answered]
How do I generate Person table?
Answer #1:
This wonderful post gets me 2/3rds of the way there. For the one-to-many tables, I'm set. Here's the code:
[add autonumber field to OriginalTable, name it PersonId]
[create empty Person table with Id, Name, MailingAddress, HomePhone fields]
INSERT INTO Person (Id, Name, MailingAddress, HomePhone)
SELECT o.PersonID, o.PersonName, o.MailingAddress, o.HomePhone
FROM OriginalTable as o
WHERE o.PersonName Is Not Null;
Question #2: [attempted] (better version by #Branko in Accepted Answer)
How do I generate Instrument table?
Answer #2:
Again, one-to-many. At first, the multiple columns had me stumped.
The solution came in two parts:
I'd just have to repeat the INSERT command, once for each column.
Using this post and the IN operator, I can check each time to confirm I hadn't already inserted that value.
Here's the code:
[create empty Instrument table with Id[autonumber], Name fields]
INSERT INTO Instrument (Name)
SELECT Distinct o.Instrument_1
FROM OriginalTable as o
WHERE o.Instrument_1 Is Not Null
AND o.Instrument_1 Not In (SELECT Name from Instrument);
INSERT INTO Instrument (Name)
SELECT Distinct o.Instrument_2
FROM OriginalTable as o
WHERE o.Instrument_2 Is Not Null
AND o.Instrument_2 Not In (SELECT Name from Instrument);
INSERT INTO Instrument (Name)
SELECT Distinct o.Instrument_3
FROM OriginalTable as o
WHERE o.Instrument_3 Is Not Null
AND o.Instrument_3 Not In (SELECT Name from Instrument);
Question #3: [unanswered]
How do I generate Person_plays_Instrument table?

Answer 1

Assuming there is OriginalTable.PersonID, which you haven't shown us, but is implied by your own answer #1, the answer #3 can be expressed simply as:
INSERT INTO Person_plays_Instrument (PersonId, InstrumentId)
SELECT PersonID, Instrument.Id
FROM
OriginalTable
JOIN Instrument
ON OriginalTable.Instrument_1 = Instrument.Name
OR OriginalTable.Instrument_2 = Instrument.Name
OR OriginalTable.Instrument_3 = Instrument.Name;
BTW, there is a more concise way to express the answer #2:
INSERT INTO Instrument (Name)
SELECT *
FROM (
SELECT o.Instrument_1 I
FROM OriginalTable as o
UNION
SELECT o.Instrument_2
FROM OriginalTable as o
UNION
SELECT o.Instrument_3
FROM OriginalTable as o
) Q
WHERE I IS NOT NULL;
And here is a fully working SQL Fiddle example for MS SQL Server. Other DBMSes should behave similarly. BTW, you should tag your question appropriately to indicate your DBMS.