How to extract this specific substring in SQL Server?

Question

I have a string with a specific pattern:

23;chair,red [$3]

i.e., a number followed by a semicolon, then a name followed by a left square bracket.

Assuming the semicolon ; always exists and the left square bracket [ always exists in the string, how do I extract the text between (and not including) the ; and the [ in a SQL Server query? Thanks.

Answer 1

Combine the SUBSTRING(), LEFT(), and CHARINDEX() functions.

SELECT LEFT(SUBSTRING(YOUR_FIELD,
                      CHARINDEX(';', YOUR_FIELD) + 1, 100),
                      CHARINDEX('[', YOUR_FIELD) - 1)
FROM YOUR_TABLE;

This assumes your field length will never exceed 100, but you can make it smarter to account for that if necessary by employing the LEN() function. I didn't bother since there's enough going on in there already, and I don't have an instance to test against, so I'm just eyeballing my parentheses, etc.

Answer 2

Assuming they always exist and are not part of your data, this will work:

declare @string varchar(8000) = '23;chair,red [$3]'
select substring(@string, charindex(';', @string) + 1, charindex(' [', @string) - charindex(';', @string) - 1)

Answer 3

An alternative to the answer provided by @Marc

SELECT SUBSTRING(LEFT(YOUR_FIELD, CHARINDEX('[', YOUR_FIELD) - 1), CHARINDEX(';', YOUR_FIELD) + 1, 100)
FROM YOUR_TABLE
WHERE CHARINDEX('[', YOUR_FIELD) > 0 AND
    CHARINDEX(';', YOUR_FIELD) > 0;

This makes sure the delimiters exist, and solves an issue with the currently accepted answer where doing the LEFT last is working with the position of the last delimiter in the original string, rather than the revised substring.