Extract email address from string using tsql

Question

I\'m trying to extract email addresses from an existing comments field and put it into its own column. The string may be something like this \"this is an example comment wit

Answer 1

You can search for '@' in the string. Then you get the string at the LEFT and RIGHT side of '@'. You then want to REVERSE the LEFT side and get first occurrence of ' ' then get the SUBSTRING from there. Then REVERSE it to get the original form. Same principle apply to the RIGHT side without doing REVERSE.

Example string: 'some text someemail@domain.org some text'

1. LEFT = 'some text someemail'
2. RIGHT = '@domain.org some text'
3. Reverse LEFT = 'liameemos txet emos'
4. SUBSTRING up to the first space = 'liameemos'
5. REVERSE(4) = someemail
6. SUBSTRING (2) up to the first space = '@domain.org'
7. Combine 5 and 6 = 'someemail@domain.org'

Your query would be:

;WITH CteEmail(email) AS(
    SELECT 'someemail@domain.org' UNION ALL
    SELECT 'some text someemail@domain.org some text' UNION ALL
    SELECT 'no email'
)
,CteStrings AS(
    SELECT
        [Left] = LEFT(email, CHARINDEX('@', email, 0) - 1),
        Reverse_Left = REVERSE(LEFT(email, CHARINDEX('@', email, 0) - 1)),
        [Right] = RIGHT(email, CHARINDEX('@', email, 0) + 1)
    FROM CteEmail
    WHERE email LIKE '%@%'
)
SELECT *,
    REVERSE(
        SUBSTRING(Reverse_Left, 0, 
            CASE
                WHEN CHARINDEX(' ', Reverse_Left, 0) = 0 THEN LEN(Reverse_Left) + 1
                ELSE CHARINDEX(' ', Reverse_Left, 0)
            END
        )
    )
    +
    SUBSTRING([Right], 0,
        CASE
            WHEN CHARINDEX(' ', [Right], 0) = 0 THEN LEN([Right]) + 1
            ELSE CHARINDEX(' ', [Right], 0)
        END
    )
FROM CteStrings

Sample Data:

email
----------------------------------------
someemail@domain.org
some text someemail@domain.org some text
no email

Result

---------------------
someemail@domain.org
someemail@domain.org