TSQL One sequence of characters must follow another - tsql

Question

First time question but thought I would see if anyone has a clear idea how to do this. Thank you.
I have a view that contains information about procedures in a hospital. Usual name and date fields and then there is a field that contains all the associated procedures that are concatenated into a single field and pipe delimited. Procedure codes are usually 4 digits and represent each individual procedure completed.
E.g. Name, DateOfBirth,|W822|W833|Z846|Z942|||||||||||||||||||||||||||||||||||||
Procedure codes starting W833,W834,W835 should always be followed by a site code (where on the body the proc was carried out) Z00-Z93 or Z95-Z99
However, it may have a Y code in between (Y282,...) the W and the Z code
There may also be a Z94* following the Y* code
How could you construct a query to find incorrect procedures.
I assume the best way would be a rather convoluted CASE statement. Anyone have any other suggestions?
Thank you.

Answer 1

If you just want to get rows where the procedure codes are in the wrong order you could use a function to validate your procedure codes:
CREATE FUNCTION fn_ValidateOrder ( #InputString NVARCHAR(MAX), #Delimiter NCHAR(1))
RETURNS BIT
AS
BEGIN
DECLARE #Valid BIT = 0, #Errors INT
/* Table to hold splitt string */
DECLARE #T TABLE (id INT IDENTITY(1,1),Val NVARCHAR(128) NULL)
INSERT INTO #T
SELECT value FROM STRING_SPLIT(#InputString,#Delimiter) WHERE value != ''
/* Validated order */
;WITH rn AS (
SELECT
ROW_NUMBER() OVER (ORDER BY val) AS rn
,id,
val
FROM #T
)
/* Count errors */
SELECT #Errors=SUM(CASE WHEN id IS NOT NULL THEN 1 ELSE 0 END) FROM rn WHERE id!=rn
/* Set return value */
IF #Errors>0
SET #Valid=0
ELSE
SET #Valid=1
RETURN #Valid
END
I used the following test data to validate:
/* Test Data*/
DECLARE #data TABLE (DateOfBirth VARCHAR(6),ProcedureCode VARCHAR(MAX))
INSERT INTO #data (DateOfBirth,ProcedureCode)
VALUES ('010176','|W822|W833|Z846|Z942|||||||||||||||||||||||||||||||||||||'),
('120176','|W822|Z282|W833|Z846|Z942|||||||||||||||||||||||||||||||||||||')
/* Validated test data */
SELECT
DateOfBirth,
dbo.fn_ValidateOrder(ProcedureCode,'|') AS ValidOrder,
ProcedureCode
FROM #data
WHERE dbo.fn_ValidateOrder(ProcedureCode,'|') = 0
Note that this will only work on SQL 2016 and newer, as the function use SPLIT_STRING.