CASE where a lot of text needs trimming - tsql

Question

I have an output in my queries that gives me:
xxxxxxx xxxxxxxxx : 123456 (xx) - xxxxxxx...
or
xxxxxxx xxxxxxxxx : 12345678 (xx) - xxxxxxx...
basically text before either a 6 or 8 digit number then text after.
Ideally I'd like to be able to CASE this column so I'd have an output where it's a 6 digit number = London and the output when it's an 8 digit number = Paris.
But I am very stuck on how to get the CASE statement to achieve this - essentially trim out a lot of text, work out if the number is either 6 or 8 digits long, then tell me if it's London or Paris. I'm not sure if it's possible.
Is this sort of CASE statement achievable? Advise / pointers would be very gratefully received. Thanks very much.

Answer 1

One way to do it is using a common table expression with patindex.
First, create and populate sample table (Please save us this step in your future questions)
DECLARE #T As Table
(
LongText varchar(4000)
)
INSERT INTO #T (LongText) VALUES
('.njauaerigha n uaer gauer 345 gnaehn 123456 (43) smgmshmsrtmh s;s nt;srtn ;nbtugarg '),
('asdfasdfasdf 12345678 (65) asdfag gr 34 6sd 64 fasd fasdfas d fasdfasdf asdf'),
('zxcvzxcvzx34cv zxcvzxcv zxcv zxcv zxcv zcxvz xcv z3 45 xcvzxcz dfg dv df df zfd zdf b 654321 (77)'),
('87654321 (99) n;arng an ; ualerg trhrt srth str sth strh ssth'),
('snhs tgnn ang nu g;arug aegaerlhae s ;5 afnauierhga.ngae489tj 8q3y .sn.5yn b.s n .5hy 5');
Then, the common table expression to get the start index of the 8/6 digit number:
WITH CTE AS
(
SELECT LongText,
PATINDEX('%[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9] ([0-9][0-9])%', LongText) As Long,
PATINDEX('%[0-9][0-9][0-9][0-9][0-9][0-9] ([0-9][0-9])%', LongText) As Short
FROM #T
)
Then, select with a couple of case expressions to extract the number and get the city:
SELECT CASE
WHEN Long > 0 THEN SUBSTRING(LongText, Long, 13)
WHEN Short > 0 THEN SUBSTRING(LongText, Short, 11)
END As Number,
CASE
WHEN Long > 0 THEN 'Paris'
WHEN Short > 0 THEN 'London'
END As City,
LongText
FROM CTE
Results:
Number City LongText
123456 (43) London .njauaerigha n uaer gauer 345 gnaehn 123456 (43) smgmshmsrtmh s;s nt;srtn ;nbtugarg
12345678 (65) Paris asdfasdfasdf 12345678 (65) asdfag gr 34 6sd 64 fasd fasdfas d fasdfasdf asdf
654321 (77) London zxcvzxcvzx34cv zxcvzxcv zxcv zxcv zxcv zcxvz xcv z3 45 xcvzxcz dfg dv df df zfd zdf b 654321 (77)
87654321 (99) Paris 87654321 (99) n;arng an ; ualerg trhrt srth str sth strh ssth
NULL NULL snhs tgnn ang nu g;arug aegaerlhae s ;5 afnauierhga.ngae489tj 8q3y .sn.5yn b.s n .5hy 5