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Mysql: Select rows from a table that are not in another
... this only works as expected when none of the columns have NULL values. In MySQL NULL != NULL so every row that has a NULL value will be returned even if there is a duplicate row in the second table.
– Kyle Kochis
Apr 7 '15 at 2:49
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Rails 3: Get Random Record
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Thing.first(:order => "RANDOM()") # For MySQL :order => "RAND()", - thanx, @DanSingerman
# Rails 3
Thing.order("RANDOM()").first
or
Thing.first(:offset => rand(Thing.count))
# Rails 3
Thing.offset(rand(Thing.count)).first
Actually, in Rails 3 all example...
简单谈谈软件配置管理 - 项目管理 - 清泛网 - 专注C/C++及内核技术
...软件过程及其软件产品的跟踪能力。即：怎么命名？版本如何设置？放到哪里？哪些是受控的？受控的级别是什么？读写的权限是什么？
2、配置变更控制
IEEE中的定义：通过建立产品基线，控制软件产品的发布和在整个软件生...
Remove Primary Key in MySQL
... following table schema which maps user_customers to permissions on a live MySQL database:
12 Answers
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Generate GUID in MySQL for existing Data?
I've just imported a bunch of data to a MySQL table and I have a column "GUID" that I want to basically fill down all existing rows with new and unique random GUID's.
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how to convert a string to date in mysql?
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As was told at MySQL Using a string column with date text as a date field, you can do
SELECT STR_TO_DATE(yourdatefield, '%m/%d/%Y')
FROM yourtable
You can also handle these date strings in WHERE clauses. For example
SELECT whatever...
How to delete duplicates on a MySQL table?
I need to DELETE duplicated rows for specified sid on a MySQL table.
25 Answers
25...
When and why are database joins expensive?
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MySQL, Oracle, SQL Server, Sybase, postgreSQL,etc. care not the order of joins. I've worked with DB2 and it also, to my knowledge, doesn't care what order you put them in. This is not helpful advice in the general case
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MySQL Cannot Add Foreign Key Constraint
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lol same. MySQL could use more precise error handling on this kind of stuff.
– dave
Apr 17 at 23:38
add a comm...
What scalability problems have you encountered using a NoSQL data store? [closed]
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I've switched a small subproject from MySQL to CouchDB, to be able to handle the load. The result was amazing.
About 2 years ago, we've released a self written software on http://www.ubuntuusers.de/ (which is probably the biggest German Linux community website)....