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Counting null and non-null values in a single query
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This works for Oracle and SQL Server (you might be able to get it to work on another RDBMS):
select sum(case when a is null then 1 else 0 end) count_nulls
, count(a) count_not_nulls
from us;
Or:
select count(*) - count(a), count(a) fro...
Regular expression to match DNS hostname or IP Address?
Does anyone have a regular expression handy that will match any legal DNS hostname or IP address?
21 Answers
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Save PL/pgSQL output from PostgreSQL to a CSV file
...ing easy to re-use or automate, you can use Postgresql's built in COPY command. e.g.
Copy (Select * From foo) To '/tmp/test.csv' With CSV DELIMITER ',' HEADER;
This approach runs entirely on the remote server - it can't write to your local PC. It also needs to be run as a Postgres "superuser" (no...
Why can't I define a default constructor for a struct in .NET?
...t have a constructor with no parameters. According to this post this is mandated by the CLI specification. What happens is that for every value-type a default constructor is created (by the compiler?) which initialized all members to zero (or null ).
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i18n Pluralization
... }
}
}
}
}
Native speakers may enjoy cases such as 111 and 121.
And here the test results:
zero: 0 запросов/куриц/яблок
one: 1 запрос/курица/яблоко
few: 3 запроса/курицы/яблока
many: 5 запросов/куриц/яблок...
How to make a flat list out of list of lists?
...for item in sublist]
As evidence, you can use the timeit module in the standard library:
$ python -mtimeit -s'l=[[1,2,3],[4,5,6], [7], [8,9]]*99' '[item for sublist in l for item in sublist]'
10000 loops, best of 3: 143 usec per loop
$ python -mtimeit -s'l=[[1,2,3],[4,5,6], [7], [8,9]]*99' 'sum(l...
How do I create a crontab through a script
...a text file with the job configured, then copy it to the cron spool folder and make sure it has the right permissions (600).
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What is the difference between save and insert in Mongo DB?
What is the difference between save and insert in Mongo DB?
both looks the same
9 Answers
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How to get IP address of the device from code?
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This is my helper util to read IP and MAC addresses. Implementation is pure-java, but I have a comment block in getMACAddress() which could read the value from the special Linux(Android) file. I've run this code only on few devices and Emulator but let me kno...
Multiple Inheritance in C#
...ern directly. But sometimes it would be helpful to have this ability.
C# and the .net CLR have not implemented MI because they have not concluded how it would inter-operate between C#, VB.net and the other languages yet, not because "it would make source more complex"
MI is a useful concept, the ...