sql server concating or replacing, which one is better (faster) - sql

Question

I have to generate a very long procedure every time for a reporting system, so i created a template for my procedure and replacing the parts are needed to, but i could do it with Concat or +(&)
for example:
set #query = '... and (
--#InnerQueries
)'
set #query = replace(#query,'--#InnerQueries',#otherValues)
vs
set #query += ' and exists (...)'
if(#xxx is not null)
set #query += 'and not exists (...)'
with replace approach it's more readable and maintainable for me, but for sake of optimization, what about Concat and attaching string together?
with replace: there are a lot of searching but less string creation
and with concat: lot's of string creation but no searching
so any idea?

Answer 1

I assume you're talking about using CONCAT or REPLACE to build an SQL then run it. If ultimately you'll process fewer than 100 REPLACEments, I'd go with that approach rather than CONCAT because it's more readable.
If however, you're talking about using concat/replace to create report output data and you will e.g. be carrying out 100 REPLACE operations per row on a million rows, I'd do the CONCAT route

Answer 2

update 2:
there could be something missing here:
if i change first variable :#sourceText_Replace
to a max value of 8000 character, and continue to add to it:
set #sourceText_Replace += '8000 character length'
set #sourceText_Replace +=#sourceText_Replace
set #sourceText_Replace +=#sourceText_Replace
set #sourceText_Replace +=#sourceText_Replace
set #sourceText_Replace +=#sourceText_Replace
set #sourceText_Replace +=#sourceText_Replace
set #sourceText_Replace +=#sourceText_Replace
it works fine, even if go up until: 16384017 character length
so any idea here is as good as mine
orginal answer:
to summarize (and if i didnt make any mistakes):
if you are searching in a long text, dont even think about using replace, it took seconds not milliseconds, but for concat obviously does not make any difference
in the blew code, in first try(small text), i just used variables default values and did not append to them,
but for second try(long Text) , i just append result from previous loop run
for long text, i did not bothered to run the loop more than 20 time, because it took over minutes.
smallText: set #destSmallText_Replace =
longText: set #destSmallText_Replace +=
here is the code for test:
SET NOCOUNT ON
drop table if exists #tempReplace
drop table if exists #tempConcat
create table #tempReplace
(
[txt] nvarchar(max) not null
)
create table #tempConcat
(
[txt] nvarchar(max) not null
)
declare #sourceText_Replace nvarchar(max) = 'small1 text to replace #textToBeReplaced after param text'
declare #text_Replace nvarchar(max) = #sourceText_Replace
declare #textToSearch nvarchar(max) = '#textToBeReplaced'
declare #textToReplace nvarchar(max) = 'textToBeReplaced'
declare #concat_Start nvarchar(max) = 'small1 text to replace'
declare #concat_End nvarchar(max) = 'after param text'
declare #text_Concat nvarchar(max) = #concat_Start
declare #whileCounter int =0
declare #maxCounter int = 5
declare #startTime datetime = getdate();
declare #endTime datetime = getdate();
begin
set #startTime = getDate();
while(#whileCounter <=#maxCounter)
begin
--long text
set #text_Replace += replace(#sourceText_Replace,#textToSearch,#textToReplace + convert(nvarchar(10), #whileCounter)) + #textToSearch
--small text
--set #text_Replace = replace(#sourceText_Replace,#textToSearch,#textToReplace + convert(nvarchar(10), #whileCounter)) + #textToSearch
--print #destSmallText_Replace
insert into #tempReplace values(#text_Replace)
set #whileCounter+=1
end
set #endTime = getDate();
print 'passedTime ' + Convert(nvarchar(20), DATEPART(millisecond, #endTime) - DATEPART(millisecond, #startTime))
end
begin
set #whileCounter = 0;
set #startTime = getDate();
while(#whileCounter <=#maxCounter)
begin
set #text_Concat += concat(#concat_Start,#textToReplace + convert(nvarchar(10), #whileCounter),#concat_End) + #textToSearch
--print #sourceSmallText_Concat
insert into #tempConcat values(#text_Concat)
set #whileCounter+=1
end
set #endTime = getDate();
print 'passedTime ' + Convert(nvarchar(20), DATEPART(millisecond, #endTime) - DATEPART(millisecond, #startTime))
end