T-SQL Calculate the max value from an Alpha Numeric key - sql

Question

I have a customers table which has an Alphanumeric key consisting of 5 letters and 3 numbers.
I'm trying to calculate the next 3 digit number in sequence for each 5 letters for example:
Example Key
ALPHA001
ALPHA002
NUMBE001
NUMBE002
NUMBE003
PREST001
PREST002
PREST003
PREST004
PREST005
From the list of keys above i'd like to return the maximum of each unique 5 letter key. i.e.
Returned Values
ALPHA002
NUMBE003
PREST005

Answer 1

First of all: Do not store more than one value within one column. should store the key and the running number in separate columns and combine them just for display purpose...
Try this
DECLARE #mockupTable TABLE(ID INT IDENTITY,YourKey VARCHAR(100));
INSERT INTO #mockupTable VALUES
('ALPHA001')
,('ALPHA002')
,('NUMBE001')
,('NUMBE002')
,('NUMBE003')
,('PREST001')
,('PREST002')
,('PREST003')
,('PREST004')
,('PREST005');
WITH cte AS
(
SELECT *
,ROW_NUMBER() OVER(PARTITION BY LEFT(YourKey,5) ORDER BY CAST(RIGHT(YourKey,3) AS INT) DESC) AS PartitionedRowNumber
FROM #mockupTable
)
SELECT *
FROM cte
WHERE PartitionedRowNumber =1;
The result
ID Key
2 ALPHA002
5 NUMBE003
10 PREST005

Answer 2

You can use row_number():
select top (1) with ties t.*
from table t
order by row_number() over (partition by left(col, patindex('%[0-9]%', col)) order by col desc);
If the letters are fixed then just use left() :
order by row_number() over (partition by left(col, 5) order by col desc);

Answer 3

I'm trying to calculate the next 3 digit number in sequence for each 5
letters
This should do it:
SELECT CONCAT(LEFT(k, 5), FORMAT(MAX(RIGHT(k, 3)) + 1, '000'))
FROM (VALUES
('ALPHA001'),
('ALPHA002'),
('NUMBE001'),
('NUMBE002'),
('NUMBE003'),
('PREST001'),
('PREST002'),
('PREST003'),
('PREST004'),
('PREST005')
) tests(k)
GROUP BY LEFT(k, 5)

Answer 4

You can do this with GROUP BY and MAX:
SELECT KeyPrefix = LEFT(ExampleKey, 5),
NextKey = CONCAT(LEFT(ExampleKey, 5),
RIGHT(CONCAT('000', MAX(CONVERT(INT, RIGHT(ExampleKey, 3))) + 1), 3))
FROM (VALUES
('ALPHA001'), ('ALPHA002'), ('NUMBE001'), ('NUMBE002'), ('NUMBE003'),
('PREST001'), ('PREST002'), ('PREST003'), ('PREST004'), ('PREST005')
) t (ExampleKey)
GROUP BY LEFT(ExampleKey, 5);
The key operations being:
Get number part of key: RIGHT(ExampleKey, 3)
Convert this to an integer: CONVERT(INT, <output from 1>)
Find the max for the key type and add 1: MAX(<output from 2>) + 1
Pad this with zeros: RIGHT(CONCAT('000', MAX(<output from 3>), 3)
Concatenate withthe original prefix: CONCAT(LEFT(ExampleKey, 5), <output from 4>)
I would however highly recommed storing this in two columns, and use a computed column to combine then:
CREATE TABLE dbo.T
(
KeyPrefix CHAR(5) NOT NULL,
KeySequence INT NOT NULL,
TKey AS CONCAT(KeyPrefix, RIGHT(CONCAT('000', KeySequence), 3))
);
Then your query becomes much simpler:
SELECT KeyPrefix,
KeySequence = MAX(KeySequence) + 1,
TKey = CONCAT(KeyPrefix, RIGHT(CONCAT('000', MAX(KeySequence) + 1), 3))
FROM (VALUES
('ALPHA', 1), ('ALPHA', 2), ('NUMBE', 1), ('NUMBE', 2), ('NUMBE', 3),
('PREST', 1), ('PREST', 2), ('PREST', 3), ('PREST', 4), ('PREST', 5)
) t (KeyPrefix, KeySequence)
GROUP BY KeyPrefix;
Although worth noting that you would never actually need to reconstruct the key as I have done above in the column TKey, you just need the max keysequence.

Answer 5

Use this query.
GO
;WITH cte AS
(
SELECT ROW_NUMBER() OVER(PARTITION BY LEFT(YourKey,patindex('%[0-9]%', YourKey)) ORDER BY CAST(RIGHT(YourKey,patindex('%[A-Z]%', YourKey)) AS INT) DESC) AS rr , YourKey FROM #mockupTable
)
SELECT YourKey FROM cte WHERE rr =1;
GO