SQL - Two Columns into One Distinct Ordered Column - sql

Question

If I have a table like this:
Col 1 | Col 2
-------------
A | 1
A | 2
B | 1
C | 1
C | 2
C | 3
How can I write a query to pull one column that looks like this --
Col 1
------
A
1
2
B
1
C
1
2
3

Answer 1

SELECT col1
FROM Some_Table_You_Did_Not_Name
UNION ALL
SELECT col2
FROM Some_Table_You_Did_Not_Name
If the order matters in your example then you want this:
WITH data AS
(
SELECT col1, col2, ROW_NUMBER() OVER (ORDER BY col1, col2) as RN
FROM Some_Table_You_Did_Not_Name
)
SELECT col
FROM (
SELECT DISTINCT col1 as col, RN, 1 as O
FROM data
UNION ALL
SELECT DISTINCT col2 as col, RN, 2 as O
FROM data
) JC_IS_THAT_GUY
ORDER BY RN ASC, O ASC, col ASC

Answer 2

You can use a query like the following:
SELECT Col1
FROM (
SELECT DISTINCT Col1, Col1 AS Col2, 0 AS grp
FROM mytable
UNION ALL
SELECT Col2 AS Col1, Col1 AS Col2, 1 AS grp
FROM mytable) AS t
ORDER BY Col2, grp, Col1
Demo here

Answer 3

There is absolutely no need to do a UNION, UNION ALL or reference the table more than once to unpivot data...
-- if Col2 is always a well ordered sequense like the test data...
SELECT
Col1 = x.Value
FROM
#TestData td
CROSS APPLY ( VALUES (IIF(td.Col2 = 1, td.Col1, NULL)), (CAST(td.Col2 AS CHAR(1))) ) x (Value)
WHERE
x.Value IS NOT NULL;
-- if it isn't...
WITH
cre_Add_RN AS (
SELECT
td.Col1,
td.Col2,
RN = ROW_NUMBER() OVER (PARTITION BY td.Col1 ORDER BY td.Col2)
FROM
#TestData td
)
SELECT
x.Value
FROM
cre_Add_RN arn
CROSS APPLY ( VALUES (IIF(arn.RN = 1, arn.Col1, NULL)), (CAST(arn.Col2 AS CHAR(1))) ) x (Value)
WHERE
x.Value IS NOT NULL;
HTH,
Jason