how to use onle only one repalce function instead of nested replace function?

Hi Expert,

I am using this below   3 replace function to replace 3 characters.
can i do only  in one replace function or any other function.

select replace(replace(replace(facility_name, '\', '\\\\'), '''', '\'''), '"', '\\"') from facility
 
 Thanks
 Thomos
deve_thomosAsked:
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slightwv (䄆 Netminder) Commented:
>>how i will do with regular expression??

As I said, I don't know if you can.  That is why I said 'might' be able to.

Off the top of my head I can't think of the expression to do what you want in a single call.

Even if an Expert here comes up with one, why would you want to see it it there is a strong possibility it will be a lot slower?
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slightwv (䄆 Netminder) Commented:
Other than "you just want to", what is the real need to do this?

The execution time of a single replace is pretty small.

You 'might' be able to do it with regular expressions (but I don't see how right now) but those types of function calls are expensive and three normal ones will probably be faster.
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deve_thomosAuthor Commented:
Hello Expert ,
how i will do with regular expression??
can you please tell me ?
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sdstuberCommented:
you can't do it with regular expressions either, at least not with Oracle's versions of them.
You'd have to use 3 expressions which, would be worse than what you have.

With a more sophisticated regexp parser, such as those in php and perl, it might be possible; but again, at the expense of performance.
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sdstuberCommented:
if you're worried simply about the cosmetic aspect of having 3 function calls, you could always write your own function that performed the 3 replaces for you but only exposed one function call.

That's obviously worse; but cosmetic reason is the only reason I can think of even wanting to try.
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slightwv (䄆 Netminder) Commented:
I can't get everything into a single regexp_replace but I can combine the quotes and get it down to two replaces, one regular and one regular expression.

Below is a test case that tests the two.

Pay particular attention the the extreme number of the loop count.  I'm running this on my home PC and had to use such a large number to get something to show a difference.

The entire test case on my PC is 7 seconds.

100 Million executions on a standard PC and they are still both close in execution times...  Do you really need to remove the three replace calls?

declare
	facility_name varchar2(100) := 'abc\def''ghi"jkl';
	new_str varchar2(100);
	start_time timestamp;
begin

start_time := systimestamp;
for i in 1..100000000 loop
	new_str := replace( replace( replace( facility_name, '\', '\\\\'), '''', '\'''), '"', '\\"');
end loop;

dbms_output.put_line(systimestamp - start_time);


start_time := systimestamp;
for i in 1..100000000 loop
	new_str := regexp_replace(replace(facility_name,'\','\\\\'), '([''"])','\\\1' );
end loop;
dbms_output.put_line(systimestamp - start_time);


end;
/

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sdstuberCommented:
I don't get the correct results with the regexp


SELECT REGEXP_REPLACE(REPLACE(facility_name, '\', '\\\\'), '([''"])', '\\\1') regrep,
       REPLACE(REPLACE(REPLACE(facility_name, '\', '\\\\'), '''', '\'''), '"', '\\"') rep3
  FROM (SELECT 'abc\def''ghi"jkl' facility_name FROM DUAL);


abc\\\\def\'ghi\"jkl   -- regexp
vs
abc\\\\def\'ghi\\"jkl   -- rep3


the regexp is dropping a slash
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slightwv (䄆 Netminder) Commented:
deve_thomos,
Please confirm that a single quote is replaced with \' and a double quote is replace with \\".

This doesn't seem correct to me when escaping certain characters.
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sdstuberCommented:
If you're wondering if "just one extra slash" makes a difference - YES!

The reason 3 expressions are needed is because there is no consistent pattern between your 3 inputs and your 3 outputs.

If you change the rules of patterns by just one character it's a whole new problem.
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slightwv (䄆 Netminder) Commented:
Even if my test case with only two replaces was a little off, it still confirms my original post in http:#a39805065 

What you have is probably the fastest way to get what you want.

It looks like there really is no other way given those specific requirements and even if there was, it wouldn't be 'better'.
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sdstuberCommented:
>>> What you have is probably the fastest way to get what you want.

agreed, and, in my opinion, the easiest to read and understand.  

You have 3 things to replace, so you replace 3 times.  It's quite logical as-is, as well as being the most efficient.
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awking00Commented:
Can you provide some sample data and what your expected output would be?
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awking00Commented:
Let me first be sure of what you're trying to do. It looks like you want to replace every backslash with four backslashes, replace every single quote with a backslash and a single quote, and replace every double quote with two backslashes and a double quote. Is that correct?
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deve_thomosAuthor Commented:
Yes ...
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slightwv (䄆 Netminder) Commented:
>>Yes ...

I believe this has been answered:  three replaces is likely the best method to do this.

You haven't posted back why you do not want to do it this way.
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