You might need to work out how long a string is. There are two ways you could measure the length of a string. The first is the number of characters; the second is the number of bytes (i.e. the amount of data).
You can see both here:
Even though I've provided a Chinese string, LEN still returns 2 as the number of characters in the string.
But because they were each two-byte characters, the function DATALENGTH returns 4 as the total number of bytes.
One of the challenges with the LEN function is that it ignore trailing spaces. So the string 'hello' and the string 'hello ' are both length 5 according to the LEN function.
If you would prefer a function that returns the actual number of characters, including trailing spaces, I'd suggest you look at the StringLength function in our free SDU Tools for developers and DBAs.
It's worth your while becoming proficient in SQL. If you'd like to learn a lot about T-SQL in a hurry, our Writing T-SQL Queries for SQL Server course is online, on-demand, and low cost.