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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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Deep null checking, is there a better way?
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}
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...
How to work around the lack of transactions in MongoDB?
...know whether this comes from my limited viewpoint (I have only worked with SQL databases so far), or whether it actually can't be done.
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What is the most ridiculous pessimization you've seen? [closed]
... ad hoc Access connections to the production DB. Nothing like a few casual SQL'ers to forget a WHERE clause and deadlock the main tables!
– HardCode
Mar 28 '09 at 5:09
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