Receiving duplicated results from UNION in SQL - sql

Question

I use SQL Server I use the following code:
CREATE TABLE table1
(
ID VARCHAR(10) NOT NULL PRIMARY KEY,
Name VARCHAR(3) NOT NULL,
Price INTEGER NOT NULL,
Date DATE
);
INSERT INTO table1 (ID, Name, Price, Date)
VALUES ('000212', 'Rod', 200, NULL);
CREATE TABLE table2
(
Descr VARCHAR(10) NOT NULL PRIMARY KEY,
Identity VARCHAR(10) NOT NULL,
amount INTEGER NOT NULL
);
INSERT INTO table2 (Descr, Identity, amount)
VALUES ('Silver rod', '000212', 3);
CREATE TABLE table3
(
Type VARCHAR(5) NOT NULL PRIMARY KEY,
Price INTEGER,
Condition INTEGER NOT NULL,
CatalogNum VARCHAR(10) NOT NULL
);
INSERT INTO table3 (Type, Price, Condition, CatalogNum)
VALUES ('Metal', NULL, 8, '000212');
INSERT INTO table3 (Type, Price, Condition, CatalogNum)
VALUES ('Wood', 300, 1, '000313');
WITH IdList AS
(
SELECT ID AS MasterId
FROM table1
UNION
SELECT Identity
FROM table2
UNION
SELECT CatalogNum
FROM table3
)
SELECT
i.MasterID,
t1.*,
t2.*,
t3.*
FROM
IdList as i
LEFT JOIN
table1 as t1 ON t1.ID = i.MasterID
LEFT JOIN
table2 as t2 ON t2.Identity = i.MasterID
LEFT JOIN
table3 as t3 ON t3.CatalogNum = i.MasterID;
SQL Fiddle demo
In order to combine several tables with the same product ID.
However for some reason I get multiple duplicated results. I.E. instead of getting one row with unique ID, I get 7 (I currently have 7 tables unlike the code above, but not necessarily - I also get 2, and 3 duplicated rows) with the same result.
Just to mention, this is a code which I found here and just edited and added 7 tables instead of only three that in the example above.