大约有 12,000 项符合查询结果（耗时：0.0247秒） [XML]
ActiveRecord.find(array_of_ids), preserving order
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Oddly, no one has suggested something like this:
index = Something.find(array_of_ids).group_by(&:id)
array_of_ids.map { |i| index[i].first }
As efficient as it gets besides letting SQL backend do it.
Edit: To improve on my own answer, you can also do it like this:
S...
Oracle Differences between NVL and Coalesce
...on of branch filters when search contains comparison of nvl result with an indexed column.
create table tt(a, b) as
select level, mod(level,10)
from dual
connect by level<=1e4;
alter table tt add constraint ix_tt_a primary key(a);
create index ix_tt_b on tt(b);
explain plan for
select * from t...
How can I set the value of a DropDownList using jQuery?
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If you working with index you can set the selected index directly with .attr():
$("#mydropdownlist").attr('selectedIndex', 0);
This will set it to the first value in the droplist.
Edit:
The way I did it above used to work. But it seems like ...
MD5 algorithm in Objective-C
... char *resultData = malloc(CC_MD5_DIGEST_LENGTH * 2 + 1);
for (uint index = 0; index < CC_MD5_DIGEST_LENGTH; index++) {
resultData[index * 2] = HexEncodeChars[(result[index] >> 4)];
resultData[index * 2 + 1] = HexEncodeChars[(result[index] % 0x10)];
}
resultDa...
What special characters must be escaped in regular expressions?
...x Flavors (PCRE)
Includes C, C++, Delphi, EditPad, Java, JavaScript, Perl, PHP (preg), PostgreSQL, PowerGREP, PowerShell, Python, REALbasic, Real Studio, Ruby, TCL, VB.Net, VBScript, wxWidgets, XML Schema, Xojo, XRegExp.PCRE compatibility may vary
Anywhere: . ^ $ * + - ? ( ) [ ] { } \ |
Leg...
Replace all spaces in a string with '+' [duplicate]
...ll(Source, stringToFind, stringToReplace) {
var temp = Source;
var index = temp.indexOf(stringToFind);
while (index != -1) {
temp = temp.replace(stringToFind, stringToReplace);
index = temp.indexOf(stringToFind);
}
return temp;
}
String.prototype.ReplaceAll = f...
Renaming projects in Xcode 4
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From Apple: iOS Developer Library Technical Q&A QA1625
Follow these steps to rename your application in Xcode 4.0 or later:
In Xcode, select your target under "Targets" in the project editor, then choose View > Utilities > Show File Inspector.
Xcode opens t...
Difference between the Apache HTTP Server and Apache Tomcat? [closed]
...r. A servlet, at the end, is a Java class. JSP files (which are similar to PHP, and older ASP files) are generated into Java code (HttpServlet), which is then compiled to .class files by the server and executed by the Java virtual machine.
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Is there a performance difference between CTE , Sub-Query, Temporary Table or Table Variable?
...hints, restructure the query, update statistics, use temporary tables, add indexes, and so on to get better performance.
As for your question. The performance of CTEs and subqueries should, in theory, be the same since both provide the same information to the query optimizer. One difference is th...
Naming returned columns in Pandas aggregate function? [duplicate]
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This will drop the outermost level from the hierarchical column index:
df = data.groupby(...).agg(...)
df.columns = df.columns.droplevel(0)
If you'd like to keep the outermost level, you can use the ravel() function on the multi-level column to form new labels:
df.columns = ["_".join(...