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Implementing Comments and Likes in database
...ucture
This pseudocode will get all the comments of photo with ID 5
SELECT * FROM actions
WHERE actions.id_Stuff = 5
AND actions.typeStuff="photo"
AND actions.typeAction = "comment"
This pseudocode will get all the likes or users who liked photo with ID 5
(you may use count() to ...
Removing all non-numeric characters from string in Python
How do we remove all non-numeric characters from a string in Python?
7 Answers
7
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How to save an activity state using save instance state?
... usually use this technique to store instance values for your application (selections, unsaved text, etc.).
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Compare two data.frames to find the rows in data.frame 1 that are not present in data.frame 2
...ata.frame(a = 1:3, b=letters[1:3])
require(sqldf)
a1NotIna2 <- sqldf('SELECT * FROM a1 EXCEPT SELECT * FROM a2')
And the rows which are in both data frames:
a1Ina2 <- sqldf('SELECT * FROM a1 INTERSECT SELECT * FROM a2')
The new version of dplyr has a function, anti_join, for exactly the...
Python Pandas merge only certain columns
...
You can use .loc to select the specific columns with all rows and then pull that. An example is below:
pandas.merge(dataframe1, dataframe2.iloc[:, [0:5]], how='left', on='key')
In this example, you are merging dataframe1 and dataframe2. You h...
Picking a random element from a set
... the buckets that make up the hashset, which allows us to more efficiently select a random elements. If random elements are necessary in Java, it might be worthwhile to define a custom hash set that allows the user to look under the hood. See [boost's docs][1] for a little more in this. [1] boos...
Why should we typedef a struct so often in C?
...me as a non-tag name is in (POSIX or Unix) program with the int stat(const char *restrict path, struct stat *restrict buf) function. There you have a function stat in the ordinary name space and struct stat in the tag name space.
– Jonathan Leffler
Jun 5 '16 a...
how do I query sql for a latest record date for each user
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select t.username, t.date, t.value
from MyTable t
inner join (
select username, max(date) as MaxDate
from MyTable
group by username
) tm on t.username = tm.username and t.date = tm.MaxDate
...
Get table column names in MySQL?
...DESCRIBE my_table;
Or in newer versions you can use INFORMATION_SCHEMA:
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = 'my_database' AND TABLE_NAME = 'my_table';
Or you can use SHOW COLUMNS:
SHOW COLUMNS FROM my_table;
...
How to load program reading stdin and taking parameters in gdb?
... I figured it out. For some reason I typed void main(int argc, char *argv[]) instead of "int main..." and it slipped my eye. Anyways everything works fine now; thanks for your help!
– vinc456
Jan 18 '09 at 19:04
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