大约有 37,000 项符合查询结果（耗时：0.0381秒） [XML]
Factors in R: more than an annoyance?
...a pain, but my theory is that 90% of why they're a pain is because in read.table and read.csv, the argument stringsAsFactors = TRUE by default (and most users miss this subtlety). I say they are useful because model fitting packages like lme4 use factors and ordered factors to differentially fit mod...
Why should I capitalize my SQL keywords? [duplicate]
...nk the latter is more readable. You can easily separate the keywords from table and column names, etc.
share
|
improve this answer
|
follow
|
...
What is the best way to solve an Objective-C namespace collision?
...not changing the address of the original symbol. Objective-C uses a lookup table to map class names to addresses, and it's a 1-1 mapping, so you can't have two classes with the same name. Thus, to load both classes, one of them must have their name changed. However, when other classes need to access...
String literals and escape characters in postgresql
Attempting to insert an escape character into a table results in a warning.
5 Answers
...
How can I call a custom Django manage.py command directly from a test driver?
...for a Django manage.py command that does a backend operation on a database table. How would I invoke the management command directly from code?
...
Test if lists share any items in python
...as such:
bool(set(a) & set(b))
Because sets are stored using a hash table in Python, searching them is O(1) (see here for more information about complexity of operators in Python). Theoretically, this is O(n+m) on average for n and m objects in lists a and b. But 1) it must first create sets ...
What is the difference between a database and a data warehouse?
... as Data Warehousing. This records the data from the user for history.
The tables and joins are complex since they are normalized (for RDMS). This is done to reduce redundant data and to save storage space.
Entity – Relational modeling techniques are used for RDMS database design.
Optimized for wr...
PDO's query vs execute
... execution. Which means you can do:
$sth = $db->prepare("SELECT * FROM table WHERE foo = ?");
$sth->execute(array(1));
$results = $sth->fetchAll(PDO::FETCH_ASSOC);
$sth->execute(array(2));
$results = $sth->fetchAll(PDO::FETCH_ASSOC);
They generally will give you a performance impr...
Create new user in MySQL and give it full access to one database
... - This is the command used to create users and grant rights to databases, tables, etc.
ALL PRIVILEGES - This tells it the user will have all standard privileges. This does not include the privilege to use the GRANT command however.
dbtest.* - This instructions MySQL to apply these rights for use ...
Count number of records returned by group by
... count(*) RecordsPerGroup,
COUNT(*) OVER () AS TotalRecords
from temptable
group by column_1, column_2, column_3, column_4
share
|
improve this answer
|
follow
...