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How do I design a class in Python?
...on could help you create one just as easily. Maybe you could stay: Query().select('Country').from_table('User').where('Country == "Brazil"'). It doesn't matter exactly the syntax -- that is your job! -- the key is the object is helping you hide something, in this case the data necessary to store and...
Blocks and yields in Ruby
...y:
days = ["monday", "tuesday", "wednesday", "thursday", "friday"]
# select those which start with 't'
days.select do | item |
item.match /^t/
end
=> ["tuesday", "thursday"]
Or, we can also provide a custom sort algorithm, for instance based on the string size:
days.sort do |x,...
Can't delete virtual device from Eclipse, android
...e inside [Your Device].avd folder
From Android Studio
Open AVD Manager
Select virtual device that you want to delete
Click down arrow at the end and select [Show on Disk] it will open directory
Find *.lock files and delete inside [Your Device].avd folder
After these steps it will allow you to ...
Convert data.frame column format from character to factor
...yr::mutate_if() to convert all character columns or dplyr::mutate_at() for select named character columns to factors:
library(dplyr)
# all character columns to factor:
df <- mutate_if(df, is.character, as.factor)
# select character columns 'char1', 'char2', etc. to factor:
df <- mutate_at(d...
Can I have multiple primary keys in a single table?
...hese practices, but there is nothing in the relational model that requires selecting a primary key among the candidate keys.
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How to add an auto-incrementing primary key to an existing table, in PostgreSQL?
...t have to have a placeholder for it in the Insert statement. Then a simple select * into the target table auto populated this column. Here are the two SQL statements that I used on PostgreSQL 9.6.4.
ALTER TABLE target ADD COLUMN some_column SERIAL;
INSERT INTO target SELECT * from source;
...
What to do on TransactionTooLargeException
...and application?
Using intents to share huge data, (for example, the user selects huge number of files from gallery share press share, the URIs of the selected files will be transferred using intents)
receiving bitmap files from service
waiting for android to respond back with huge data (for exampl...
Why does Hibernate require no argument constructor?
...please look at my problem How to write HQL JOIN query for multiple table's selected Columns using Constructor In The Select Clause
– Shantaram Tupe
Dec 9 '17 at 9:33
...
Convert list of dictionaries to a pandas DataFrame
...o extract only the 0th and 2nd rows from data2 above, you can use:
rows_to_select = {0, 2}
for i in reversed(range(len(data2))):
if i not in rows_to_select:
del data2[i]
pd.DataFrame(data2)
# pd.DataFrame.from_dict(data2)
# pd.DataFrame.from_records(data2)
A B C D E
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How to implement one-to-one, one-to-many and many-to-many relationships while designing tables?
...ction table
Example queries:
-- Getting all students for a class:
SELECT s.student_id, last_name
FROM student_classes sc
INNER JOIN students s ON s.student_id = sc.student_id
WHERE sc.class_id = X
-- Getting all classes for a student:
SELECT c.class_id, name
FROM s...