Trimming text strings in SQL Server 2008

Question

I have a table in a SQL Server 2008 database. This table has a nvarchar(256) column called \'Name\'. Unfortunately, the values in this field have extra spaces included. For

Answer 1

I would try something like this for a Trim function that takes into account all white-space characters defined by the Unicode Standard (LTRIM and RTRIM do not even trim new-line characters!):

IF OBJECT_ID(N'dbo.IsWhiteSpace', N'FN') IS NOT NULL
    DROP FUNCTION dbo.IsWhiteSpace;
GO

-- Determines whether a single character is white-space or not (according to the UNICODE standard).
CREATE FUNCTION dbo.IsWhiteSpace(@c NCHAR(1)) RETURNS BIT
BEGIN
	IF (@c IS NULL) RETURN NULL;
	DECLARE @WHITESPACE NCHAR(31);
	SELECT @WHITESPACE = ' ' + NCHAR(13) + NCHAR(10) + NCHAR(9) + NCHAR(11) + NCHAR(12) + NCHAR(133) + NCHAR(160) + NCHAR(5760) + NCHAR(8192) + NCHAR(8193) + NCHAR(8194) + NCHAR(8195) + NCHAR(8196) + NCHAR(8197) + NCHAR(8198) + NCHAR(8199) + NCHAR(8200) + NCHAR(8201) + NCHAR(8202) + NCHAR(8232) + NCHAR(8233) + NCHAR(8239) + NCHAR(8287) + NCHAR(12288) + NCHAR(6158) + NCHAR(8203) + NCHAR(8204) + NCHAR(8205) + NCHAR(8288) + NCHAR(65279);
	IF (CHARINDEX(@c, @WHITESPACE) = 0) RETURN 0;
	RETURN 1;
END
GO

IF OBJECT_ID(N'dbo.Trim', N'FN') IS NOT NULL
    DROP FUNCTION dbo.Trim;
GO

-- Removes all leading and tailing white-space characters. NULL is converted to an empty string.
CREATE FUNCTION dbo.Trim(@TEXT NVARCHAR(MAX)) RETURNS NVARCHAR(MAX)
BEGIN
	-- Check tiny strings (NULL, 0 or 1 chars)
	IF @TEXT IS NULL RETURN N'';
	DECLARE @TEXTLENGTH INT = LEN(@TEXT);
	IF @TEXTLENGTH < 2 BEGIN
		IF (@TEXTLENGTH = 0) RETURN @TEXT;
		IF (dbo.IsWhiteSpace(SUBSTRING(@TEXT, 1, 1)) = 1) RETURN '';
		RETURN @TEXT;
	END
	-- Check whether we have to LTRIM/RTRIM
	DECLARE @SKIPSTART INT;
	SELECT @SKIPSTART = dbo.IsWhiteSpace(SUBSTRING(@TEXT, 1, 1));
	DECLARE @SKIPEND INT;
	SELECT @SKIPEND = dbo.IsWhiteSpace(SUBSTRING(@TEXT, @TEXTLENGTH, 1));
	DECLARE @INDEX INT;
	IF (@SKIPSTART = 1) BEGIN
		IF (@SKIPEND = 1) BEGIN
			-- FULLTRIM
			-- Determine start white-space length
			SELECT @INDEX = 2;
			WHILE (@INDEX < @TEXTLENGTH) BEGIN -- Hint: The last character is already checked
				-- Stop loop if no white-space
				IF (dbo.IsWhiteSpace(SUBSTRING(@TEXT, @INDEX, 1)) = 0) BREAK;
				-- Otherwise assign index as @SKIPSTART
				SELECT @SKIPSTART = @INDEX;
				-- Increase character index
				SELECT @INDEX = (@INDEX + 1);
			END
			-- Return '' if the whole string is white-space
			IF (@SKIPSTART = (@TEXTLENGTH - 1)) RETURN ''; 
			-- Determine end white-space length
			SELECT @INDEX = (@TEXTLENGTH - 1);
			WHILE (@INDEX > 1) BEGIN 
				-- Stop loop if no white-space
				IF (dbo.IsWhiteSpace(SUBSTRING(@TEXT, @INDEX, 1)) = 0) BREAK;
				-- Otherwise increase @SKIPEND
				SELECT @SKIPEND = (@SKIPEND + 1);
				-- Decrease character index
				SELECT @INDEX = (@INDEX - 1);
			END
			-- Return trimmed string
			RETURN SUBSTRING(@TEXT, @SKIPSTART + 1, @TEXTLENGTH - @SKIPSTART - @SKIPEND);
		END 
		-- LTRIM
		-- Determine start white-space length
		SELECT @INDEX = 2;
		WHILE (@INDEX < @TEXTLENGTH) BEGIN -- Hint: The last character is already checked
			-- Stop loop if no white-space
			IF (dbo.IsWhiteSpace(SUBSTRING(@TEXT, @INDEX, 1)) = 0) BREAK;
			-- Otherwise assign index as @SKIPSTART
			SELECT @SKIPSTART = @INDEX;
			-- Increase character index
			SELECT @INDEX = (@INDEX + 1);
		END
		-- Return trimmed string
		RETURN SUBSTRING(@TEXT, @SKIPSTART + 1, @TEXTLENGTH - @SKIPSTART);
	END ELSE BEGIN
		-- RTRIM
		IF (@SKIPEND = 1) BEGIN
			-- Determine end white-space length
			SELECT @INDEX = (@TEXTLENGTH - 1);
			WHILE (@INDEX > 1) BEGIN 
				-- Stop loop if no white-space
				IF (dbo.IsWhiteSpace(SUBSTRING(@TEXT, @INDEX, 1)) = 0) BREAK;
				-- Otherwise increase @SKIPEND
				SELECT @SKIPEND = (@SKIPEND + 1);
				-- Decrease character index
				SELECT @INDEX = (@INDEX - 1);
			END
			-- Return trimmed string
			RETURN SUBSTRING(@TEXT, 1, @TEXTLENGTH - @SKIPEND);
		END 
	END
	-- NO TRIM
	RETURN @TEXT;
END
GO