大约有 30,000 项符合查询结果（耗时：0.0455秒） [XML]
DISTINCT for only one column
Let's say I have the following query.
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Rails where condition using NOT NIL
...t's easy:
Foo.includes(:bar).where.not(bars: {id: nil})
See also:
http://guides.rubyonrails.org/active_record_querying.html#not-conditions
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How to get the seconds since epoch from the time + date output of gmtime()?
...re two ways, depending on your original timestamp:
mktime() and timegm()
http://docs.python.org/library/time.html
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Emacs on Mac OS X Leopard key bindings
...th another key. By itself, it is escape.
Read the excellent article at http://stevelosh.com/blog/2012/10/a-modern-space-cadet/ for a lot more information.
Is there a Boolean data type in Microsoft SQL Server like there is in MySQL? [duplicate]
...rmation on three valued logic-
Example of three valued logic in SQL Server
http://www.firstsql.com/idefend3.htm
https://www.simple-talk.com/sql/learn-sql-server/sql-and-the-snare-of-three-valued-logic/
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How to insert a line break in a SQL Server VARCHAR/NVARCHAR string
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I found the answer here: http://blog.sqlauthority.com/2007/08/22/sql-server-t-sql-script-to-insert-carriage-return-and-new-line-feed-in-code/
You just concatenate the string and insert a CHAR(13) where you want your line break.
Example:
DECLARE @...
Why do loggers recommend using a logger per class?
As per NLog's documentation:
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How to import existing *.sql files in PostgreSQL 8.4?
...; done
Here's the documentation of the psql application (thanks, Frank): http://www.postgresql.org/docs/current/static/app-psql.html
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For each row in an R dataframe
I have a dataframe, and for each row in that dataframe I have to do some complicated lookups and append some data to a file.
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Cleanest way to build an SQL string in Java
...obtaining the SQL string, you could also just execute it, using jOOQ. See
http://www.jooq.org
(Disclaimer: I work for the company behind jOOQ)
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