Reverse Statement Word by Word in SQL server

To reverse any statement Word by Word in SQL server we could use the SUBSTRING function which allows us to extract and display the part of a string.

Pre-requisite :SUBSTRING function

Approach :

• Declared three variables (@Input, @Output, @Length) using the DECLARE statement.
• Use the WHILE Loop to iterate every character present in the @Input. For the condition inside the SQL Server while loop, use the SQL LEN Function to check whether the length of the Input is greater than 0 or not.
• Within the while loop, use the SUBSTRING Function to set the @Output value with three parameters, and they are Input, start point, endpoint. Here we assigned the Input as @Input, use the start point as 0.
• Use the CHARINDEX Function to find the ‘ ‘, so that the endpoint will be before the space.
• Now, adding this to @Output, and which is empty at the starting of the loop.
• To update the @Input variable, use the SUBSTRING Function. Here we assigned the Input as @Input.
• Next, use the SQL CHARINDEX Function to find the empty space, and then we added 1 so that the starting point will be after space.
• Then, use the SQL LEN Function to specify the end value.
• At SET @Output it is extracting the word starting at 0 indexes and up to empty space. That will be the first word.
• Once it got its first word, it will remove that word from @Input using the SET @Input code.

Input :
Welcome to SQL Server Tutorial on w3wiki.

Example –

DECLARE @Input VARCHAR(MAX)
DECLARE @Output VARCHAR(MAX)
DECLARE @Length INT 

SET @Input = 'Welcome to SQL Server 
             Tutorial on w3wiki.'

SET @Output = ''
WHILE LEN(@Input) > 0

BEGIN
IF CHARINDEX(' ', @Input) > 0

BEGIN
SET @Output = SUBSTRING
              (@Input, 0, CHARINDEX(' ', @Input))
               + ' ' + @Output
SET @Input = LTRIM
             (RTRIM
             (SUBSTRING
             (@Input, CHARINDEX 
             (' ', @Input) + 1, LEN(@Input))))
END

ELSE

BEGIN
SET @Output = @Input + ' ' + @Output
SET @Input = ''
END
END
SELECT @Output

Output :

w3wiki. on Tutorial Server SQL to Welcome

Input and Output using SQL Server Management Studio :