從Muiltiple列SELECT DISTINCT成一列

Question

我有這樣的：

ColumnA ColumnB ColumnC 
Dog  Soda  Book 
CatIce  Juice  Notebook  
Bird  Water  Pencil 
Dog  Water  Notebook 

通過使用這種選擇：

select ColumnA, ColumnB, ColumnC from table  

我想這樣的名單：

ColumnD 
Bird 
Book 
Cat 
Dog 
Ice 
Juice 
Notebook  
Pencil 
Soda 
Water 

哪有我這樣做？謝謝！

Answer 1

使用UNION

SELECT ColumnA 
FROM table 

UNION 

SELECT ColumnB 
FROM table 

UNION 

SELECT columnC 
FROM table