附加 varchar 字符串后将填充空格添加回 CHAR

Question

I have a CHAR(250) field , which , for example will initially contain 10 byte data and 240 bytes of space, so remaining it has 250-10=240 bytes . Now I wanted to append a varchar of length say 20 bytes . So it will go to 240 + 20 =260 bytes which while inserting back to CHAR field will give size overflow issue.

Can do this , but I need the actual length , that means i want to re-pad the final string , ie 250 bytes in the final length ,

DECLARE @Var CHAR(250)='var lenght initial Data'
SELECT replace(@Var,' ','')
DECLARE @TempVar VARCHAR(20) = 'new text to be added'
SET @FinalVar=@Var + @TempVar
--Need to add final padding back to make it back to 250 bytes

Is there any other way rather counting and re-adding the space pads back ?

Answer 1

This is really your expected result?

The initial value all in the left, and the new values beeing added to the right?

Answer 2

As you never tagged the DB that you have (as the sql tag info says to do), so I'm assuming MySQL/MariaDB here...

The replace is not really doing anything, but it seems that you want:
(and yes, no need to recount, by specifying a length)

DECLARE Var CHAR(250) default 'var length initial Data';
-- SELECT replace(@Var,' ',''); -- ... is not saved anywhere, so I removed.
DECLARE FinalVar CHAR(250);
SELECT CONCAT(Var, ' ', otherText) INTO FinalVar;

So, putting that into a function:

DELIMITER //

CREATE FUNCTION right_pad_spaces(otherText varchar(250)) RETURNS CHAR(250)
DETERMINISTIC
BEGIN
    DECLARE Var CHAR(250) default 'var length initial Data';
    DECLARE FinalVar CHAR(250);
    SELECT CONCAT(Var, ' ', otherText) INTO FinalVar;
    RETURN FinalVar ;
END; //

DELIMITER ;

Then use the function, RPAD the result with spaces, limited to 250 total length:

SELECT RPAD(right_pad_spaces('new text to be added'), 250, ' ') AS 'new string';

Output: (note the horizontal scroll bar)

Checking the length of the same call:

SELECT Length(
    RPAD(right_pad_spaces('new text to be added'), 250, ' ')
) AS 'total length';

Gives:

Here's a dbfiddle with that handling.
Know that the site does not use DELIMITER , so that was added for your local use.

Answer 3

So looks like there is no 'proper' fix to this but this is what I ended up with

DECLARE @Var CHAR(250)='var lenght initial Data'
SELECT @Var=replace(@Var,' ','')
DECLARE @TempVar VARCHAR(20) = 'new text to be added'
SET @FinalVar=@Var + @TempVar
SELECT @TempEmails= CAST(left(@FinalVar, 250) AS CHAR(250)) --CAST to char pads back to 250 , this is the easiest way

the Tweak is the CAST AS CHAR(250) which will re-pad the string to 250