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MySQL JOIN the most recent row only?
...virtually instantaneous (WorkBench literally says 0.000 seconds, even with sql_no_cache set), whereas doing the search in the join took multiple seconds to complete. Still baffled, but I mean you can't argue with results like that.
– Brian Leishman
Mar 21 '17 a...
ActiveRecord: size vs count
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As the other answers state:
count will perform an SQL COUNT query
length will calculate the length of the resulting array
size will try to pick the most appropriate of the two to avoid excessive queries
But there is one more thing. We noticed a case where size acts differe...
How to display unique records from a has_many through relationship?
...ou use the :uniq option on your association (as shown in my answer) or the SQL DISTINCT stmt (e.g. has_many :products, :through => :orders, :select => "DISTINCT products.*). In the first case, ALL records are fetched and rails removes the duplicates for you. In the later case, only non-duplica...
How do MySQL indexes work?
I am really interested in how MySQL indexes work, more specifically, how can they return the data requested without scanning the entire table?
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Linq to Entities join vs groupjoin
...ies in the second list.
That's why Join is the equivalent of INNER JOIN in SQL: there are no entries for C. While GroupJoin is the equivalent of OUTER JOIN: C is in the result set, but with an empty list of related entries (in an SQL result set there would be a row C - null).
Syntax
So let the two l...
Django Setup Default Logging
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Tiny correction: the comment implies sql logging would be affected by the django.request logger. To redirect sql logging, you'd define a logger for 'django.db'. The django.request logger handles 5xx & 4xx http responses.
– rych
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XPath to select multiple tags
...in general people do care about the differences between: kitchen:table and sql:table, or between architecture:column, sql:column, array:column, military:column
– Dimitre Novatchev
Aug 1 '18 at 16:14
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“媒”出路？如今“媒体+行业”创业机会多得是 - 资讯 - 清泛网 - 专注C/C+...
...渠道和平台日渐式微，更多的传播主体及传播创意被广泛使用，创新型媒体事件不断出现。
互联网技术的赋权，让更多的普通用户拥有了媒体能力，能生产媒体内容并传播出去。这种媒体内容已不仅仅是指传统意义上的文章、...
自动生成Linux下Makefile全攻略（automake原理） - C/C++ - 清泛网 - 专注C/C++及内核技术
...config.h.top ltcf-cxx.sh
Report bugs to <bug-automake@gnu.org>.
使用automake我们只需要写Makefile.am文件，指定那些目录或文件需要参与编译，生成哪些内容等：
AUTOMAKE_OPTIONS=foreign
lib_LTLIBRARIES= liblog.la
noinst_HEADERS = \
logging/LogClas...
Deep null checking, is there a better way?
...
}
It's an idea I derrived from the null coalescing operator in C# and T-SQL. The nice thing is that the return type is always the return type of the inner property.
That way you can do this:
var berries = cake.Coal(x => x.frosting).Coal(x => x.berries);
...or a slight variation of the a...