Fill with spaces a column value in update - sql-server

Question

How to automatically fill a column with spaces to a pre-determined length in update SQL sentence in SQL Server 2012?
I have a table with several columns like
Col1 NVARCHAR(10)
Col2 NVARCHAR(100)
Col3 NVARCHAR(200)
Col4 NVARCHAR(50)
and more.
If value of column is NULL or '', I update the column with spaces to a pre-determined length (the lenth of the column).
For Col3, if value is NULL or '', spaces to 200 blank space (' ')
if value has any characters, 'abcd', fill (pad right) to 200 blank spaces. Then, finally 4 not spaces characters and 196 spaces characteres.
For example, for Col1 has length 10.
1) Value = NULL , Col1 value = ' ' (10 spaces)
2) Value = '' , Col1 value = ' ' (10 spaces)
2) Value = 'abc' , Col1 value = 'abc ' (abc and 7 spaces)
How can I do that in the UPDATE SQL?
Maybe using
select column_name, data_type, character_maximum_length
from information_schema.columns
where table_name = 'myTable'
or
SELECT COL_LENGTH('Table', 'Column')
More in How to get the size of a varchar[n] field in one SQL statement?

Answer 1

Try the following, the LEFT is used to keep the length down to the column length, while the space ensures the field is filled with spaces:
create table test (col1 varchar(10), col2 varchar(15))
GO
insert into test (col1, col2)
values ('', '')
,(NULL, NULL)
,('abc', 'abc')
UPDATE test
SET col1 = LEFT(COALESCE(col1, '') + SPACE(COL_LENGTH('test', 'col1')), COL_LENGTH('test', 'col1'))
,col2 = LEFT(COALESCE(col2, '') + SPACE(COL_LENGTH('test', 'col2')), COL_LENGTH('test', 'col2'))
FROM test
SELECT *
FROM test

Answer 2

I don't understand what you want exactly, but here is what I understand:
CREATE TABLE MyTable (
Col1 NVARCHAR(200),
Col2 NVARCHAR(100),
Col3 NVARCHAR(200),
Col4 NVARCHAR(50)
);
INSERT INTO MyTable VALUES (NULL, NULL, NULL, NULL), ('ABC', NULL, NULL, NULL);
-- You can do the same for the other cols
UPDATE MyTABLE
SET Col1 = REPLICATE(' ', COL_LENGTH('MyTable', 'Col1')/2)
WHERE Col1 IS NULL;
SELECT *
FROM MyTable;
Demo
Update:
Here is how to do it in one statement:
UPDATE MyTABLE
SET Col1 = (SELECT CASE WHEN (Col1 IS NULL) OR (Col1 = '') THEN
REPLICATE(' ', COL_LENGTH('MyTable', 'Col1')/2)
ELSE Col1 + REPLICATE(' ', (COL_LENGTH('MyTable', 'Col1')/2)- LEN(Col1)) END),
Col2 = (SELECT CASE WHEN (Col2 IS NULL) OR (Col2 = '') THEN
REPLICATE(' ', COL_LENGTH('MyTable', 'Col2')/2)
ELSE Col2 + REPLICATE(' ', (COL_LENGTH('MyTable', 'Col2')/2)- LEN(Col2)) END),
Col3 = (SELECT CASE WHEN (Col3 IS NULL) OR (Col3 = '') THEN
REPLICATE(' ', COL_LENGTH('MyTable', 'Col1')/2)
ELSE Col3 + REPLICATE(' ', (COL_LENGTH('MyTable', 'Col3')/2)- LEN(Col3)) END),
Col4 = (SELECT CASE WHEN (Col4 IS NULL) OR (Col4 = '') THEN
REPLICATE(' ', COL_LENGTH('MyTable', 'Col4')/2)
ELSE Col4 + REPLICATE(' ', (COL_LENGTH('MyTable', 'Col4')/2)- LEN(Col4)) END);
Demo