SQL: Replacing dates contained within a text string - sql

Question

I am using SQL Server Management Studio 2012. I work with medical records and need to de-identify reports. The reports are structured in a table with columns Report_Date, Report_Subject, Report_Text, etc... The string I need to update is in report_text and there are ~700,000 records.
So if I have:
"patient had an EKG on 04/09/2012"
I need to replace that with:
"patient had an EKG on [DEIDENTIFIED]"
I tried
UPDATE table
SET Report_Text = REPLACE(Report_Text, '____/___/____', '[DEIDENTIFED]')
because I need to replace anything in there that looks like a date, and it runs but doesn't actually replace anything, because apparently I can't use the _ wildcard in this command.
Any recommendations on this? Advance thanks!

Answer 1

You can use PATINDEX to find the location of Date and then use SUBSTRING and REPLACE to replace the dates.
Since there may be multiple dates in the Text you have to run a while loop to replace all the dates.
Below sql will work for all dates in the form of MM/DD/YYYY
WHILE EXISTS( SELECT 1 FROM dbo.MyTable WHERE PATINDEX('%[0-9][0-9]/[0-9][0-9]/[0-9][0-9][0-9][0-9]%',Report_Text) > 0 )
BEGIN
UPDATE t
SET Report_Text = REPLACE(Report_Text, DateToBeReplaced, '[DEIDENTIFIED]')
FROM ( SELECT * ,
SUBSTRING(Report_Text,PATINDEX('%[0-9][0-9]/[0-9][0-9]/[0-9][0-9][0-9][0-9]%',Report_Text), 10) AS DateToBeReplaced
FROM dbo.MyTable AS a
WHERE PATINDEX('%[0-9][0-9]/[0-9][0-9]/[0-9][0-9][0-9][0-9]%',Report_Text) > 0
) AS t
END
I have tested the above sql on a dummy table with few rows.I don't know how it will scale for your data but recommend you to give it a try.

Answer 2

To keep it simple, assume that a number represents an identifying element in the string so look for the position of the first number in the string and the position of the last number in the string. Not sure if this will apply to your entire set of records but here is the code ...
I created two test strings ... the one you supplied and one with the date at the beginning of the string.
Declare #tstString varchar(100)
Set #tstString = 'patient had an EKG on 04/09/2012'
Set #tstString = '04/09/2012 EKG for patient'
Select #tstString
-- Calculate 1st Occurrence of a Number
,PATINDEX('%[0-9]%',#tstString)
-- Calculate last Occurrence of a Number
,LEN(#tstString) - PATINDEX('%[0-9]%',REVERSE(#tstString))
,CASE
-- No numbers in the string, return the string
WHEN PATINDEX('%[0-9]%',#tstString) = 0 THEN #tstString
-- Number is the first character to find the last position and remove front
WHEN PATINDEX('%[0-9]%',#tstString) = 1 THEN
CONCAT('[DEIDENTIFIED]',SUBSTRING(#tstString, LEN(#tstString)-PATINDEX('%[0-9]%',REVERSE(#tstString))+2,LEN(#tstString)))
-- Just select string up to the first number
ELSE CONCAT(SUBSTRING(#tstString,1,PATINDEX('%[0-9]%',#tstString)-1),'[DEIDENTIFIED]')
END AS 'newString'
As you can see, this is messy in SQL.
I would rather achieve this with a parser service and move the data with SSIS and call the service.