大约有 47,000 项符合查询结果（耗时：0.0601秒） [XML]
Get index of array element faster than O(n)
...gt; [6] }
This allows for a quick search for duplicate entries:
indices.select { |k, v| v.size > 1 }
=> { 1 => [0, 3], 2 => [1, 4], 3 => [2, 5] }
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Is the SQL WHERE clause short-circuit evaluated?
...y use this for optional parameters. Is this the same as short circuiting?
SELECT [blah]
FROM Emp
WHERE ((@EmpID = -1) OR (@EmpID = EmpID))
This gives me the option to pass in -1 or whatever to account for optional checking of an attribute. Sometimes this involves joining on multiple tables, ...
Save Screen (program) output to a file
...
The selected answer doesn't work quite well with multiple sessions and doesn't allow to specify a custom log file name.
For multiple screen sessions, this is my formula:
Create a configuration file for each process:
logfile t...
Options, Settings, Properties, Configuration, Preferences — when and why?
...
Settings: Thinking of a slider to select a value from 1 to 10 for example
Options: Thinking of an on/off button
Preferences: Thinking of a choice from multiple choices, like morning, afternoon or evening
Configuration: Technical settings probably end users...
How to recover MySQL database from .myd, .myi, .frm files
...ql\data\foldername\.mydfiles
Then visit localhost/phpmyadmin in a browser. Select the database you have just pasted into the mysql\data folder, and click on Export in the navigation bar. Chooses the export it as a .sql file. It will then pop up asking where the save the file
And that is it! You (s...
ERROR 1452: Cannot add or update a child row: a foreign key constraint fails
... table. Following query would be helpful to fetch those non-matching rows:
SELECT child_table.*
FROM child_table
LEFT JOIN parent_table
ON parent_table.referenced_column = child_table.referencing_column
WHERE parent_table.referenced_column IS NULL
Now, you can generally do one (or more) of th...
Postgis installation: type “geometry” does not exist
...ing following code
CREATE EXTENSION postgis;
In detail,
open pgAdmin
select (click) your database
click "SQL" icon on the bar
run "CREATE EXTENSION postgis;" code
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Laravel Check If Related Model Exists
...method calls through to an Eloquent query Builder, which is set up to only select the related objects. That Builder in turn passes unknown method calls through to its underlying query Builder.
This means you can use the exists() or count() methods directly from a relation object:
$model->relati...
MongoDB: How to update multiple documents with a single command?
...{field1: 'field1', field2: 'field2'})
New in version 3.2
Params::
{}: select all records updated
Keyword argument multi not taken
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What is an ORM, how does it work, and how should I use one? [closed]
...anually, you would do something like that:
book_list = new List();
sql = "SELECT book FROM library WHERE author = 'Linus'";
data = query(sql); // I over simplify ...
while (row = data.next())
{
book = new Book();
book.setAuthor(row.get('author');
book_list.add(book);
}
With an ORM ...