提取名字和姓氏

Question

I have a column named Name in a table called test which has Full name and I am trying to extract First name and Last Name. So I wrote query something like this:

SELECT 
[Name],
 LEFT([Name],CHARINDEX(' ',[Name])-1)  AS FIRST_NAME,
SUBSTRING([Name],CHARINDEX(' ',[Name])+1,LEN([Name])) AS LAST_NAME
FROM Test

But It is giving me error saying:

Msg 537, Level 16, State 2, Line 1 Invalid length parameter passed to the LEFT or SUBSTRING function.

Thta's because I have some values in the name like:

Name:

Hopkins

How do I handle these?

Answer 1

Declare @t table ( [Name] varchar(100) )

insert into @t ( Name )
VALUES ( 'dennis hopper' ), ('keanu reaves'), ('thatgirl') 

SELECT
    [Name],
    CHARINDEX(' ', [Name]),
    CASE WHEN CHARINDEX(' ', [Name]) > 0 THEN
        LEFT([Name],CHARINDEX(' ',[Name])-1)
    ELSE
        [Name]
    END as FIRST_NAME,
    CASE WHEN CHARINDEX(' ', [Name]) > 0 THEN
        SUBSTRING([Name],CHARINDEX(' ',[Name])+1, ( LEN([Name]) - CHARINDEX(' ',[Name])+1) )
    ELSE
        NULL
    END as LAST_NAME
FROM @t

Answer 2

The problem with your original code is here:

CHARINDEX(' ',[Name])-1

If [Name] does not contain a space, CharIndex returns 0. You subtract 1 and feed this in to the Left function. When the 2nd parameter to the left function is -1, you will get this error. In my opinion, the easiest way to "fix" this problem is to give the CharIndex function something to find, like this:

CHARINDEX(' ',[Name] + ' ')-1

Now... this code cannot fail.

You only NEED to do this one place in your original code, but you should add it to the LAST_NAME part also. If you don't, you will get incorrect results (eventhough you will not get an error).

SELECT [Name],
       LEFT([Name],CHARINDEX(' ',[Name] + ' ')-1)  AS FIRST_NAME,
       SUBSTRING([Name],CHARINDEX(' ',[Name] + ' ')+1,LEN([Name])) AS LAST_NAME
FROM   Test

This query will return the same results as the query suggested by @Sage, but (in my opinion) it is easier to read, and easier to understand.

Answer 3

we may also use locate function

SELECT Name, LEFT(Name,locate(' ',Name)-1) AS FIRST_NAME, SUBSTRING(Name,locate(' ',Name)+1,LENgth(Name)) AS LAST_NAME FROM test