SQL change a string using a pattern - sql

Question

I need to do something special in SQL, I don't know if a standard function exists, I actually don't know what to search... ! So any advice would be appreciated.
Here is my problem:
I have a data which is a number: 7000000
And I have a "formatting pattern": ****5**
My goal is to merge both: result for this example is: 7000500
(a star means to keep the original value, and a number means to change it)
another example:
7894321
*0**9*1
-------
7094921
(I use SQL Server)

Answer 1

This task can be performed in any programming language with basic for-loop and and some internal functions to find substring and replace
Here is how it's done in SQL SERVER (given that the string and the format is of same length)
Create your own function
CREATE FUNCTION dbo.Formatter
(
#str NVARCHAR(MAX),
#format NVARCHAR(MAX)
)
RETURNS NVARCHAR(MAX)
AS
BEGIN
DECLARE #i int = 1, #len int = LEN(#str)
-- Iterates over over each char in the FORMAT and replace the original string if applies
WHILE #i <= #len
BEGIN
IF SUBSTRING(#format, #i, 1) <> '*'
SET #str = STUFF(#str, #i, 1, SUBSTRING(#format, #i, 1))
SET #i = #i + 1
END
RETURN #str
END
USE your function in your SELECTs, e.g.
DECLARE #str VARCHAR(MAX) = '7894321'
DECLARE #format VARCHAR(MAX) = '*0**9*1'
PRINT('Format: ' + #format)
PRINT('Old string: ' + #str)
PRINT('New string: ' + dbo.Formatter(#str, #format))
Result:
Format: *0**9*1
Old string: 7894321
New string: 7094921

Answer 2

I would split the string into it's individual characters, use a CASE expression to determine what character should be retained, and then remerge. I'm going to assume you're on a recent version of SQL Server, and thus have access to STRING_AGG; if not, you'll want to use the "old" FOR XML PATH method. I also assume a string of length 10 of less (if it's more, then just increase the size of the tally).
DECLARE #Format varchar(10) = '****5**';
WITH Tally AS(
SELECT V.I
FROM (VALUES(1),(2),(3),(4),(5),(6),(7),(8),(9),(10))V(I))
SELECT STRING_AGG(CASE SSf.C WHEN '*' THEN SSc.C ELSE SSf.C END,'') WITHIN GROUP (ORDER BY T.I) AS NewString
FROM (VALUES(1,'7894321'),(2,'7000000'))YT(SomeID,YourColumn) --This would be your table
JOIN Tally T ON LEN(YT.YourColumn) >= T.I
CROSS APPLY (VALUES(SUBSTRING(YT.YourColumn,T.I,1)))SSc(C)
CROSS APPLY (VALUES(SUBSTRING(#Format,T.I,1)))SSf(C)
GROUP BY YT.SomeID;
db<>fiddle

Answer 3

If your value is an int and your format is an int also, then you can do this:
DECLARE #formatNum int = CAST(REPLACE(#format, '*', '0') AS int);
SELECT f.Formatted
FROM Table
CROSS APPLY (
SELECT Formatted = SUM(CASE
WHEN ((#FormatNum / Base) % 10) > 0
THEN ((#FormatNum / Base) % 10) * Base
ELSE ((t.MyNumber / Base) % 10) * Base END
FROM (VALUES
(10),(100),(1000),(10000),(100000),(1000000),(10000000),(100000000),(1000000000)
) v(Base)
) f
The / is integer division, % is modulo, so dividing a number by Base and taking the modulo 10 will give you exactly one digit.