T-SQL Space Before Capital Letters - tsql

Question

The question is self explanatory. Could you please point out a way to put spaces between each capital letter of a string.
SELECT dbo.SpaceBeforeCap('ThisIsATestString')
would result in
This Is A Test String.

Answer 1

This will add spaces only if the previous and next character is lowercase. That way 'MyABCAnalysis' will be 'My ABC Analysis'.
I added a check for a previous space too. Since some of our strings are prefixed with 'GR_' and some also contain underscores, we can use the replace function as follows:
select dbo.GR_SpaceBeforeCap(replace('GR_ABCAnalysis_Test','_',' '))
Returns 'GR ABC Analysis Test'
CREATE FUNCTION GR_SpaceBeforeCap (
#str nvarchar(max)
)
returns nvarchar(max)
as
begin
declare
#i int, #j int
, #cp nchar, #c0 nchar, #c1 nchar
, #result nvarchar(max)
select
#i = 1
, #j = len(#str)
, #result = ''
while #i <= #j
begin
select
#cp = substring(#str,#i-1,1)
, #c0 = substring(#str,#i+0,1)
, #c1 = substring(#str,#i+1,1)
if #c0 = UPPER(#c0) collate Latin1_General_CS_AS
begin
-- Add space if Current is UPPER
-- and either Previous or Next is lower
-- and Previous or Current is not already a space
if #c0 = UPPER(#c0) collate Latin1_General_CS_AS
and (
#cp <> UPPER(#cp) collate Latin1_General_CS_AS
or #c1 <> UPPER(#c1) collate Latin1_General_CS_AS
)
and #cp <> ' '
and #c0 <> ' '
set #result = #result + ' '
end -- if #co
set #result = #result + #c0
set #i = #i + 1
end -- while
return #result
end

Answer 2

Assuming SQL Server 2005 or later, this modified from code taken here: http://www.kodyaz.com/articles/case-sensitive-sql-split-function.aspx
CREATE FUNCTION SpaceBeforeCap
(
#str nvarchar(max)
)
returns nvarchar(max)
as
begin
declare #i int, #j int
declare #returnval nvarchar(max)
set #returnval = ''
select #i = 1, #j = len(#str)
declare #w nvarchar(max)
while #i <= #j
begin
if substring(#str,#i,1) = UPPER(substring(#str,#i,1)) collate Latin1_General_CS_AS
begin
if #w is not null
set #returnval = #returnval + ' ' + #w
set #w = substring(#str,#i,1)
end
else
set #w = #w + substring(#str,#i,1)
set #i = #i + 1
end
if #w is not null
set #returnval = #returnval + ' ' + #w
return ltrim(#returnval)
end
This can then be called just as you have suggested above.

Answer 3

This function combines previous answers. Selectively choose to preserve adjacent CAPS:
CREATE FUNCTION SpaceBeforeCap (
#InputString NVARCHAR(MAX),
#PreserveAdjacentCaps BIT
)
RETURNS NVARCHAR(MAX)
AS
BEGIN
DECLARE
#i INT, #j INT,
#previous NCHAR, #current NCHAR, #next NCHAR,
#result NVARCHAR(MAX)
SELECT
#i = 1,
#j = LEN(#InputString),
#result = ''
WHILE #i <= #j
BEGIN
SELECT
#previous = SUBSTRING(#InputString,#i-1,1),
#current = SUBSTRING(#InputString,#i+0,1),
#next = SUBSTRING(#InputString,#i+1,1)
IF #current = UPPER(#current) COLLATE Latin1_General_CS_AS
BEGIN
-- Add space if Current is UPPER
-- and either Previous or Next is lower or user chose not to preserve adjacent caps
-- and Previous or Current is not already a space
IF #current = UPPER(#current) COLLATE Latin1_General_CS_AS
AND (
#previous <> UPPER(#previous) COLLATE Latin1_General_CS_AS
OR #next <> UPPER(#next) collate Latin1_General_CS_AS
OR #PreserveAdjacentCaps = 0
)
AND #previous <> ' '
AND #current <> ' '
SET #result = #result + ' '
END
SET #result = #result + #current
SET #i = #i + 1
END
RETURN #result
END
GO
SELECT dbo.SpaceBeforeCap('ThisIsASampleDBString', 1)
GO
SELECT dbo.SpaceBeforeCap('ThisIsASampleDBString', 0)

Answer 4

CLR and regular expressions or 26 replace statements a case sensitive collate clause and a trim.

Answer 5

Another strategy would be to check the ascii value of each character:
create function SpaceBeforeCap
(#str nvarchar(max))
returns nvarchar(max)
as
begin
declare #result nvarchar(max)= left(#str, 1),
#i int = 2
while #i <= len(#str)
begin
if ascii(substring(#str, #i, 1)) between 65 and 90
select #result += ' '
select #result += substring(#str, #i, 1)
select #i += 1
end
return #result
end
/***
SELECT dbo.SpaceBeforeCap('ThisIsATestString')
**/

Answer 6

To avoid loops altogether, use of a tally table can help here. If you are running on SQL 2022, then the generate_series function can remove even this dependency. This method will be significantly faster than iterating through a loop.
create function core.ufnAddSpaceBeforeCapital
(
#inputString nvarchar(max)
)
returns nvarchar(max)
as
begin
declare #outputString nvarchar(max)
select
#outputString = string_agg(iif(t.value = 1, upper(substring(#inputString,t.value,1)),iif(ascii(substring(#inputString,t.value,1)) between 65 and 90, ' ','') + substring(#inputString,t.value,1)),'')
from
generate_series(1,cast(len(#inputString) as int)) t
return #outputString
end
The scalar function is not inlineable, so I've provided an alternative inline table-valued function if that's what you need.
create function core.ufnAddSpaceBeforeCapitalITVF
(
#inputString nvarchar(max)
)
returns table
as
return
(
select
string_agg(iif(t.value = 1, upper(substring(#inputString,t.value,1)),iif(ascii(substring(#inputString,t.value,1)) between 65 and 90, ' ','') + substring(#inputString,t.value,1)),'') as outputString
from
generate_series(1,cast(len(#inputString) as int)) t
)
end

Answer 7

While I really like the char looping answers I was not thrilled with the performance. I have found this performs in a fraction of the time for my use case.
CREATE function SpaceBeforeCap
(#examine nvarchar(max))
returns nvarchar(max)
as
begin
DECLARE #index as INT
SET #index = PatIndex( '%[^ ][A-Z]%', #examine COLLATE Latin1_General_BIN)
WHILE #index > 0 BEGIN
SET #examine = SUBSTRING(#examine, 1, #index) + ' ' + SUBSTRING(#examine, #index + 1, LEN(#examine))
SET #index = PatIndex( '%[^ ][A-Z]%', #examine COLLATE Latin1_General_BIN)
END
RETURN LTRIM(#examine)
end
This makes use of the fact that
case sensitive pattern search only works in some collations. The character class [^ ] means anything except space, so as we add the missing spaces we match farther into the string until it is complete.