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MySQL - Rows to Columns
...temvalue |
+--------+----------+-----------+
| 1 | A | 10 |
| 1 | B | 3 |
| 2 | A | 9 |
| 2 | C | 40 |
+--------+----------+-----------+
This will be our goal, the pretty pivot table:
select * from history_itemvalue_piv...
How can I convert a DateTime to the number of seconds since 1970?
...ateTime variable to Unix time, ie, the number of seconds since Jan 1st, 1970. It looks like a DateTime is actually implemented as the number of 'ticks' since Jan 1st, 0001.
...
How can I force division to be floating point? Division keeps rounding down to 0?
... I want to calculate a / b , so if I use integer division I'll always get 0 with a remainder of a .
11 Answers
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What is a regular expression for a MAC Address?
...
The standard (IEEE 802) format for
printing MAC-48 addresses in
human-friendly form is six groups of
two hexadecimal digits, separated by
hyphens - or colons :.
So:
^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$
...
Boolean Field in Oracle
...as JDBC, OCCI, and other programming environments,
it's better to select 0 for false and 1 for true so it can work
correctly with the getBoolean and setBoolean functions.
Basically they advocate method number 2, for efficiency's sake, using
values of 0/1 (because of interoperability with JD...
How to toggle a value in Python
What is the most efficient way to toggle between 0 and 1 ?
17 Answers
17
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How do I measure execution time of a command on the Windows command line?
...
30 Answers
30
Active
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How do you add swap to an EC2 instance?
...
10 Answers
10
Active
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Pandas percentage of total with groupby
...swer:
# From Paul H
import numpy as np
import pandas as pd
np.random.seed(0)
df = pd.DataFrame({'state': ['CA', 'WA', 'CO', 'AZ'] * 3,
'office_id': list(range(1, 7)) * 2,
'sales': [np.random.randint(100000, 999999)
for _ in range(12...
Avoid trailing zeroes in printf()
...ormat specifiers. The closest you could get would be:
printf("%.6g", 359.013); // 359.013
printf("%.6g", 359.01); // 359.01
but the ".6" is the total numeric width so
printf("%.6g", 3.01357); // 3.01357
breaks it.
What you can do is to sprintf("%.20g") the number to a string buffer then man...