I have a MySQL database whose keys are of this type:
A_10
A_10A
A_10B
A_101
QAb801
QAc5
QAc25
QAd2993
I would like them to sort first by the alpha portion, then by the numeric portion, just like above. I would like this to be the default sorting of this column.
1) how can I sort as specified above, i.e. write a MySQL function?
2) how can I set this column to use the sorting routine by default?
some constraints that might be helpful: the numeric portion of my ID's never exceeds 100,000. I use this fact in some javascript code to convert my ID's to strings concatenating the non-numeric portion with the (number + 1,000,000). (At the time I had not noticed the variations/subparts as above such as A_10A, A_10B, so I'll have to revamp that part of my code.)
The best way to achieve what you want is to store each part in its own column, and I would strongly recommend to change table structure. If it's impossible, you can try the following:
Create 3 UDFs which returns prefix, numeric part, and postfix of your string. For a better performance they should be native (Mysql, as any other RDMS, is not really good in complex string parsing). Then you can call these functions in ORDER BY clause or in trigger body which validates your column. In any case, it will work slower than if you create 3 columns.
No simple answer that I know of. I had something similar a while back but had to use jQuery to sort it. So what I did was first get the output into an javascript array. Then you may want to insert a zero padding to your numbers. Separate the Alpha from Nummerics using a regex, then reassemble the array:
var zarr = new Array();
for(var i=0; i<val.length; i++){
var chunk = val[i].match(/(\d+|[^\d]+)/g).join(',');
var chunks = chunk.split(",");
for(var s=0; s<chunks.length; s++){
if(isNaN(chunks[s]) == true)
zarr.push(chunks[s]);
else
zarr.push(zeroPad(chunks[s], 5));
}
}
function zeroPad(num,count){
var numZeropad = num + '';
while(numZeropad.length < count) {
numZeropad = "0" + numZeropad;
}
return numZeropad;
}
You'll end up with an array like this:
A_00100
QAb00801
QAc00005
QAc00025
QAd02993
Then you can do a natural sort. I know you may want to do it through straight MySQL but I am not to sure if it does natural sorting.
Good luck!
Related
I am sorry if this is a beginner's question.
I made some Arrays named like map01, map02 and so on... As you can see, I'm making a tile-based flash here. And I need to make a function that when you input a number like: createmap(1); it will get the variable map01 and use the information.
Can I do anything like: var temp:Array = Array(["map" + valueInput]);??
Please tell me if you need anything more.
First, instead of having variables with indices in their names, you should create an array of them. Here, an array of arrays.
So you just have to call var temp:Array = maps[valueInput] as Array;.
If you really don't want to do that and stick with your n variables, you can write
var index:String = valueInput.toString();
if (index.length == 1)
index = "0" + index; //have the index on two digits "01", "02"
var temp:Array = this["map" + index];
Note that it will only work for your 99 first variables (oh God...)
I guess a step back is in order. My original question is at the bottom of this post for reference.
I am writing a word guessing game and wanted a way to:
1. Given a word length of 2 - 10 characters, randomly generate a valid english word to guess
2.given a 2 - 10 character guess, ensure that it is a valid english word.
I created a vector of 9 objects, one for each word length and dynamically created 172000
property/ value pairs using the words from a word list to name the properties and setting their value to true. The inner loop is:
for (i = 0; i < _WordCount[wordLength] - 2; i)
{
_WordsList[wordLength]["" + _WordsVector[wordLength][i++]] = true;
}
To validate a word , the following lookup returns true if valid:
function Validate(key:String):Boolean
{
return _WordsList[key.length - 2][key]
}
I transferred them from a vector to objects to take advantage of the hash take lookup of the properties. Haven't looked at how much memory this all takes but it's been a useful learning exercise.
I just wasn't sure how best to randomly choose a property from one of the objects. I was thinking of validating whatever method I chose by generating 1000 000 words and analyzing the statistics of the distribution.
So I suppose my question should really first be am I better off using some other approach such as keeping the lists in vectors and doing a search each time ?
Original question
Newbie first question:
I read a thread that said that traversal order in a for.. in is determined by a hash table and appears random.
I'm looking for a good way to randomly select a property in an object. Would the first element in a for .. in traversing the properties, or perhaps the random nth element in the iteration be truly random. I'd like to ensure that there is approximately an equal probability of accessing a given property. The Objects have between approximately 100 and 20000 properties. Other approaches ?
thanks.
Looking at the scenario you described in your edited question, I'd suggest using a Vector.<String> and your map object.
You can store all your keys in the vector and map them in the object, then you can select a random numeric key in the vector and use the result as a key in the map object.
To make it clear, take a look at this simple example:
var keys:Vector.<String> = new Vector.<String>();
var map:Object = { };
function add(key:String, value:*):void
{
keys.push(key);
map[key] = value;
}
function getRandom():*
{
var randomKey = keys[int(Math.random() * keys.length)];
return map[randomKey];
}
And you can use it like this:
add("a", "x");
add("b", "y");
add("c", "z");
var radomValue:* = getRandom();
Using Object instead of String
Instead of storing the strings you can store objects that have the string inside of them,
something like:
public class Word
{
public var value:String;
public var length:int;
public function Word(value:String)
{
this.value = value;
this.length = value.length;
}
}
Use this object as value instead of the string, but you need to change your map object to be a Dictionary:
var map:Dictionary = new Dictionary();
function add(key:Word, value:*):void
{
keys.push(key);
map[key] = value;
}
This way you won't duplicate every word (but will have a little class overhead).
I'm preparing data for a datatable in Linq2Sql
This code highlights as a 'Possible multiple enumeration of IEnumerable' (in Resharper)
// filtered is an IEnumerable or an IQueryable
var total = filtered.Count();
var displayed = filtered
.Skip(param.iDisplayStart)
.Take(param.iDisplayLength).ToList();
And I am 100% sure Resharper is right.
How do I rewrite this to avoid the warning
To clarify, I get that I can put a ToList on the end of filtered to only do one query to the Database eg.
var filteredAndRun = filtered.ToList();
var total = filteredAndRun.Count();
var displayed = filteredAndRun
.Skip(param.iDisplayStart)
.Take(param.iDisplayLength).ToList();
but this brings back a ton more data than I want to transport over the network.
I'm expecting that I can't have my cake and eat it too. :(
It sounds like you're more concerned with multiple enumeration of IQueryable<T> rather than IEnumerable<T>.
However, in your case, it doesn't matter.
The Count call should translate to a simple and very fast SQL count query. It's only the second query that actually brings back any records.
If it is an IEnumerable<T> then the data is in memory and it'll be super fast in any case.
I'd keep your code exactly the same as it is and only worry about performance tuning when you discover you have a significant performance issue. :-)
You could also do something like
count = 0;
displayed = new List();
iDisplayStop = param.iDisplayStart + param.iDisplayLength;
foreach (element in filteredAndRun) {
++count;
if ((count < param.iDisplayStart) || (count > iDisplayStop))
continue;
displayed.Add(element);
}
That's pseudocode, obviously, and I might be off-by-one in the edge conditions, but that algorithm gets you the count with only a single iteration and you have the list of displayed items only at the end.
I'm attempting to alter the contents of certain parts of a HTML form through usage of the URL. For a text field, I'm aware that this will suffice,
http://<domain>?fieldname=ping&anotherfield=pong
On the form there are multiple select braces (drop down boxes); Is it possible to pick an int or string value through the url for this?
There seems to be little documentation on this (or even people trying to do the same)...
You haven't specified how you want to do this, but I'll assume that you want to use JavaScript:
To get a value from QueryString:
getQueryStringArgument = function(key) {
var hu = window.location.search.substring(1);
var gy = hu.split("&");
for (i = 0; i < gy.length; i++) {
var ft = gy[i].split("=");
if (ft[0] == key)
return ft[1];
}
}
To set the selected value of the select list:
document.getElementById("sel").value = getQueryStringArgument("id");
For a text field, I'm aware that this will suffice
No, it won't (at least, not in a generic way).
For a text field, the default value is specified by the value attribute. There might be a server side script that populates it based on query string data, but there doesn't have to be.
On the form there are multiple select braces (drop down boxes); Is it possible to pick an int or string value through the url for this?
Again, this requires an attribute to be set (selected on <option>), and that could (again) be set by a server side script based on the query string data.
My problem requires me to dynamically add where clauses to a IQueryable based on user input. The problem i'm having is that Linq-to-SQL doesn't seem to like having multiple where clauses on the same field, it actually duplicates the search arg value for the last item on all parameters. I verified this behavior through a SQL trace. Here is what I'm seeing.
WHERE ([t22].[OpenText] LIKE #p11) AND ([t22].[OpenText] LIKE #p12)
-- #p11: Input NVarChar (Size = 10; Prec = 0; Scale = 0) [%classify%] // Should be 2da57652-dcdf-4cc8-99db-436c15e5ef50
-- #p12: Input NVarChar (Size = 10; Prec = 0; Scale = 0) [%classify%]
My code uses a loop to dynamically add the where clauses as you can see below. My question is how do I work around this? This pretty much seems like a bug with the tool, no?
// add dyanmic where clauses based on user input.
MatchCollection searchTokens = Helper.ExtractTokensWithinBracePairs(filterText);
if (searchTokens.Count > 0)
{
foreach(Match searchToken in searchTokens)
query = query.Where((material => material.OpenText.Contains(searchToken.Value)));
}
else
{
query = query.Where((material => material.OpenText.Contains(filterText)));
}
Closing over the loop variable considered harmful! Change
foreach(Match searchToken in searchTokens) {
query = query.Where(
material => material.OpenText.Contains(searchToken.Value)
);
}
to
foreach(Match searchToken in searchTokens) {
Match token = searchToken;
query = query.Where(
material => material.OpenText.Contains(token.Value)
);
}
You are closing over the loop variable, which is considered harmful. To fix do this:
foreach(Match searchToken in searchTokens)
{
Match searchToken2 = searchToken;
// ^^^^^^^^^^^^ copy the value of the reference to a local variable.
query = query.Where(material => material.OpenText.Contains(searchToken2.Value));
// use the copy here ^^^^^^^^^^^^
}
The reason why your version doesn't work is that the query refers to the variable searchToken, not the value it had when the query was created. When the variable's value changes, all your queries see the new value.
I don't have enough rep to leave comments yet (or this would be a comment and not an answer) but the answers listed here worked for me.
However, I had to turn off compiler optimizations in order for it to work. If you do not turn off compiler optimizations (at least at the method level) then the compiler sees you setting a loop variable to a local variable and throws the local variable away.