I have a string that has a form:
UPDATE "TABLE"."ITEMS" SET ITM_DESCR=:sqldevvalue WHERE ROWID = :sqldevgridrowid AND ORA_ROWSCN = :sqldevgridrowscn
and its binding values as:
#1(11):Test Record #2(18):AAAG9IAAFAAAC0eAAB #3(7):7746161
How can I construct a regular expression to replace the parameter names (starting with :) with their corresponding values and create a combined string that has the form:
UPDATE "TABLE"."ITEMS" SET ITM_DESCR=Test Record WHERE ROWID = AAAG9IAAFAAAC0eAAB AND ORA_ROWSCN = 7746161
Here's a very simple, naive regex:
:(\w+)
Replace the match with the value, $1 contains the parameter name.
Here's a less naive attempt:
'(?:''|[^'])*'|:(\w+)
If $1 is set, replace the match with the value ($1 contains the paramter name), else do not replace. This version will let you handle situations like WHERE column = 'some text :not_a_param more text'
And... the not naive approach is to use prepared statements and SQL parameters with whatever SQL client you're using. This is the best option as it negates any risk of SQL injections if you do something wrong, and lets the DBMS cache the execution plan for your request.
Related
Given input string as
'PARAM_1=TRUE,THRESHOLDLIST=kWh,2000,Gallons,1000,litre,3000,PARAM_2=TRUE,PARAM_3=abc,123,kWh,800,Gallons,500'
and unit_param = 'Gallons'
I need to extract value of unit_param (Gallons) which is 1000 using postgresql regex functions.
As of now, I have a function that first extracts value for THRESHOLDLIST which is "kWh,2000,Gallons,1000,litre,3000", then splits and loops over the array to get the value.
Can I get this efficiently using regex.
SELECT substring('PARAM_1=TRUE,THRESHOLDLIST=kWh,2000,Gallons,1000,litre,3000,PARAM_2=TRUE,PARAM_3=abc,123,xyz' FROM '%THRESHOLDLIST=#".........#",%' FOR '#')
Use substring() with the target input grouped:
substring(myCol, 'THRESHOLDLIST=[^=]*Gallons,([0-9]+)')
The expression [^=]* means “characters that are not =”, so it won’t match Gallons within another parameter.
select
Substring('PARAM_1=TRUE,THRESHOLDLIST=kWh,2000,Gallons,1000,litre,3000,PARAM_2=TRUE,PARAM_3=abc,123,xyz' from 'Gallons,\d*');
returns Gallons,1000
I'm trying to replace parts of a string that contains what should be dates, but which are possibly in an impermissible format. Specifically, all of the dates are in the form "mm/dd/YYYY" and they need to be in the form "YYYY-mm-dd". One caveat is that the original dates may not exactly be in the mm/dd/YYYY format; some are like "5/6/2015". For example, if
val x = "where date >= '05/06/2017'"
then
x.replaceAll("'([0-9]{1,2})/([0-9]{1,2})/([0-9]{4})'", "'$3-$1-$2'")
performs the desired replacement (returns "2017-05-06"), but for
val y = "where date >= '5/6/2017'"
this does not return the desired replacement (returns "2017-5-6" -- for me, an invalid representation). With the Joda Time wrapper nscala-time, I've tried capturing the dates and then reformatting them:
import com.github.nscala_time.time.Imports._
import org.joda.time.DateTime
val f = DateTimeFormat.forPattern("yyyy-MM-dd")
y.replaceAll("'([0-9]{1,2}/[0-9]{1,2}/[0-9]{4})'",
"'"+f.print(DateTimeFormat.forPattern("MM/dd/yyyy").parseDateTime("$1"))+"'")
But this fails with a java.lang.IllegalArgumentException: Invalid format: "$1". I've also tried using the f interpolator and padding with 0s, but it doesn't seem to like that either.
Are you not able to do additional processing on the captured groups ($1, etc.) inside the replaceAll? If not, how else can I achieve the desired result?
The $1 like backreferences can only be used inside string replacement patterns. In your code, "$1" is not a backreference any longer.
You may use a "callback" with replaceAllIn to actually get the match object and access its groups to further manipulate them:
val pattern = "'([0-9]{1,2}/[0-9]{1,2}/[0-9]{4})'".r
y = pattern replaceAllIn (y, m => "'"+f.print(DateTimeFormat.forPattern("MM/dd/yyyy").parseDateTime(m.group(1)))+"'")
Regex.replaceAllIn is overloaded and can take a Match => String.
I am trying to extract a substring from a text column using a regular expression, but in some cases, there are multiple instances of that substring in the string.
In those cases, I am finding that the query does not return the first occurrence of the substring. Does anyone know what I am doing wrong?
For example:
If I have this data:
create table data1
(full_text text, name text);
insert into data1 (full_text)
values ('I 56, donkey, moon, I 92')
I am using
UPDATE data1
SET name = substring(full_text from '%#"I ([0-9]{1,3})#"%' for '#')
and I want to get 'I 56' not 'I 92'
You can use regexp_matches() instead:
update data1
set full_text = (regexp_matches(full_text, 'I [0-9]{1,3}'))[1];
As no additional flag is passed, regexp_matches() only returns the first match - but it returns an array so you need to pick the first (and only) element from the result (that's the [1] part)
It is probably a good idea to limit the update to only rows that would match the regex in the first place:
update data1
set full_text = (regexp_matches(full_text, 'I [0-9]{1,3}'))[1]
where full_text ~ 'I [0-9]{1,3}'
Try the following expression. It will return the first occurrence:
SUBSTRING(full_text, 'I [0-9]{1,3}')
You can use regexp_match() In PostgreSQL 10+
select regexp_match('I 56, donkey, moon, I 92', 'I [0-9]{1,3}');
Quote from documentation:
In most cases regexp_matches() should be used with the g flag, since
if you only want the first match, it's easier and more efficient to
use regexp_match(). However, regexp_match() only exists in PostgreSQL
version 10 and up. When working in older versions, a common trick is
to place a regexp_matches() call in a sub-select...
I am working on a db query in mongo where i need to query the document by regular expressing the string field(fieldToQuery).
the datastructure is like
{
fieldToQuery : "4052577300",
someOtherField : "some value",
...
...
}
I have the value like "804052577300", using which i have to query the above document.
How to achieve the same using $regex operator?
Update:
I need to do like ends with regex in mongo.
You could do a sort of reverse regex query where you create a regex using the fieldToQuery value and then test that against your query value:
var value = "804052577300";
db.test.find({
$where: "new RegExp(this.fieldToQuery + '$').test('" + value + "');"
});
The $where operator allows you to execute arbitrary JavaScript against each doc in your collection; where this is the current doc, and the truthy result of the expression determines whether the doc should be included in the result set.
So in this case, a new RegExp is built for each doc's fieldToQuery field with a $ at the end to anchor the search to the end of the string. The test method of the regex is then called to test whether the value string matches the regex.
The $where string is evaluated server-side, so value's value must be evaluated client-side by directly including its value into the $where string.
Note that $where queries can be quite slow as they can't use indexes.
You could do something like this:
db.collection.find({ fieldToQuery: /4052577300$/})
The regex pattern above is equivalent to the SQL's LIKE operation:
select * from table where fieldToQuery like '%4052577300' => will return the document with the value "804052577300"
Given a URL with GET arguments such as
http://www.domain.com?key1=value1+value2+value3&key2=value4+value5
I wish to capture all the values for a given key (into separate references if possible). For example if the desired key was key1 i would want to capture value1 in \1 (or $1 depending on language), value2 in \2, and value3 in \3.
My flawed regex is:
/[?&](?:key1)=((?:[^+&]+[+&$])+)/
which yields 0 results.
I am writing this in c++ using ECMA syntax, but I think I could convert a solution or advice from any regex flavor to ECMA. Any help would be appreciated.
This has been answered before and there are compact scripts written for it.
Regular expressions are not optimal for extracting query string values. At the end of this answer, I will give you an expression which can extract the value(s) for a given field into separate references. But not that it takes a "lot" of time to extract the parameters one at a time using regular expressions, but they can all be completely extracted very quickly with no regular expression engine needed. For instance, http://www.htmlgoodies.com/beyond/javascript/article.php/3755006/How-to-Use-a-JavaScript-Query-String-Parser.htm
What language are you trying to use to extract these parameters, C++?
If you are using, JavaScript, you use the small functions mentioned in the article above, i.e.,
function ptq(q)
{
/* parse the query */
var x = q.replace(/;/g, '&').split('&'), i, name, t;
/* q changes from string version of query to object */
for (q={}, i=0; i<x.length; i++)
{
t = x[i].split('=', 2);
name = unescape(t[0]);
if (!q[name])
q[name] = [];
if (t.length > 1)
{
q[name][q[name].length] = unescape(t[1]);
}
/* next two lines are nonstandard, allowing programmer-friendly Boolean parameters */
else
q[name][q[name].length] = true;
}
return q;
}
function param() {
return ptq(location.search.substring(1).replace(/+/g, ' '));
}
Once you have that code included in your page's scripts, then you can parse the current URLs data by doing query = param(); and then using the value of query.key1, etc.
You can parse other query-string formatted data by using the ptq() function directly, i.e., query_object = ptq(query_string).
If you are using another language and regular expressions are the way you want to do it, then this would return all values matching key1, for instance:
/key1=([^&;]*)/g
That will return all the values with a certain field name (which in the query string definition, are written like this, key1=value1&key1=value2&key1=value3, etc.).
The way you ask your question makes it sound like you want to create your own programmer-friendly way of supplying values (i.e., by constructing your own custom URLs rather than receiving data from form submissions through browsers) in which your values are separated by spaces (spaces are encoded as + signs in an HTTP GET query string, and as %20 in generic query strings).
You could make a complicated regular expression to do this in one step, but it is faster to match the entire field (all the values and the + signs as well), and then split the result at the + signs.
For each of the results from the regular expression I indicate, you can extract the plus-sign separated values by simply doing /[^+]*/g