What’s the best way to capitalise the first letter of each word in a string in SQL Server

From http://www.sql-server-helper.com/functions/initcap.aspx

CREATE FUNCTION [dbo].[InitCap] ( @InputString varchar(4000) ) 
RETURNS VARCHAR(4000)
AS
BEGIN

DECLARE @Index          INT
DECLARE @Char           CHAR(1)
DECLARE @PrevChar       CHAR(1)
DECLARE @OutputString   VARCHAR(255)

SET @OutputString = LOWER(@InputString)
SET @Index = 1

WHILE @Index <= LEN(@InputString)
BEGIN
    SET @Char     = SUBSTRING(@InputString, @Index, 1)
    SET @PrevChar = CASE WHEN @Index = 1 THEN ' '
                         ELSE SUBSTRING(@InputString, @Index - 1, 1)
                    END

    IF @PrevChar IN (' ', ';', ':', '!', '?', ',', '.', '_', '-', '/', '&', '''', '(')
    BEGIN
        IF @PrevChar != '''' OR UPPER(@Char) != 'S'
            SET @OutputString = STUFF(@OutputString, @Index, 1, UPPER(@Char))
    END

    SET @Index = @Index + 1
END

RETURN @OutputString

END
GO

There is a simpler/smaller one here (but doesn't work if any row doesn't have spaces, "Invalid length parameter passed to the RIGHT function."):

http://www.devx.com/tips/Tip/17608

As a table-valued function:

CREATE FUNCTION dbo.InitCap(@v AS VARCHAR(MAX))
RETURNS TABLE
AS
RETURN 
WITH a AS (
    SELECT (
        SELECT UPPER(LEFT(value, 1)) + LOWER(SUBSTRING(value, 2, LEN(value))) AS 'data()'
        FROM string_split(@v, ' ')
        ORDER BY CHARINDEX(value,@v)
        FOR XML PATH (''), TYPE) ret)

SELECT CAST(a.ret AS varchar(MAX)) ret from a
GO

Note that string_split requires COMPATIBILITY_LEVEL 130.

If you are looking for the answer to the same question in Oracle/PLSQL then you may use the function INITCAP. Below is an example for the attribute dname from a table department which has the values ('sales', 'management', 'production', 'development').

SQL> select INITCAP(dname) from department;

INITCAP(DNAME)
--------------------------------------------------
Sales
Management
Production
Development

A variation of the one I've been using for quite some time is:

CREATE FUNCTION [widget].[properCase](@string varchar(8000)) RETURNS varchar(8000) AS
BEGIN   
    SET @string = LOWER(@string)
    DECLARE @i INT
    SET @i = ASCII('a')
    WHILE @i <= ASCII('z')
    BEGIN
        SET @string = REPLACE( @string, ' ' + CHAR(@i), ' ' + CHAR(@i-32))
        SET @i = @i + 1
    END
    SET @string = CHAR(ASCII(LEFT(@string, 1))-32) + RIGHT(@string, LEN(@string)-1)
    RETURN @string
END

You can easily modify to handle characters after items other than spaces if you wanted to.

Another solution without using the loop - pure set-based approach with recursive CTE

create function [dbo].InitCap (@value varchar(max))
returns varchar(max) as
begin

    declare
        @separator char(1) = ' ',
        @result varchar(max) = '';

    with r as (
        select value, cast(null as varchar(max)) [x], cast('' as varchar(max)) [char], 0 [no] from (select rtrim(cast(@value as varchar(max))) [value]) as j
        union all
        select right(value, len(value)-case charindex(@separator, value) when 0 then len(value) else charindex(@separator, value) end) [value]
        , left(r.[value], case charindex(@separator, r.value) when 0 then len(r.value) else abs(charindex(@separator, r.[value])-1) end ) [x]
        , left(r.[value], 1)
        , [no] + 1 [no]
        from r where value > '')

    select @result = @result +
    case
        when ascii([char]) between 97 and 122 
            then stuff(x, 1, 1, char(ascii([char])-32))
        else x
    end + @separator
    from r where x is not null;

    set @result = rtrim(@result);

    return @result;
end