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MySQL: @variable vs. variable. What's the difference?
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MySQL has a concept of user-defined variables.
They are loosely typed variables that may be initialized somewhere in a session and keep their value until the session ends.
They are prepended with an @ sign, like this: @var
Yo...
CDN（内容分发网络）技术原理 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...的整个过程。CDN网络是在用户和服务器之间增加Cache层，如何将用户的请求引导到Cache上获得源服务器的数据，主要是通过接管DNS实现，下面让我们看看访问使用CDN缓存后的网站的过程：
通过上图，我们可以了解到，使用了CDN...
MySQL Update Inner Join tables query
I have no idea what the problem is. Using MySQL 5.0 I get a compile error when attempting to run the following MySQL update query:
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Best lightweight web server (only static content) for Windows [closed]
...r the Windows OS. It includes the latest versions of Apache2, Perl5, PHP5, MySQL5, phpMyAdmin and more. No installation required. No registry dust. Just unpack and fire up.
– Piotr
Apr 14 '16 at 13:35
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MySQL load NULL values from CSV data
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MySQL manual says:
When reading data with LOAD DATA
INFILE, empty or missing columns are
updated with ''. If you want a NULL
value in a column, you should use \N
in the data file. The literal word
“NULL” ma...
How to Get True Size of MySQL Database?
I would like to know how much space does my MySQL database use, in order to select a web host.
I found the command SHOW TABLE STATUS LIKE 'table_name' so when I do the query, I get something like this:
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What's the difference between utf8_general_ci and utf8_unicode_ci?
...ncoding. The differences are in how text is sorted and compared.
Note: In MySQL you have to use utf8mb4 rather than utf8. Confusingly, utf8 is a flawed UTF-8 implementation from early MySQL versions which remains only for backward compatibility. The fixed version was given the name utf8mb4.
Note: N...
Error 1046 No database Selected, how to resolve?
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You need to tell MySQL which database to use:
USE database_name;
before you create a table.
In case the database does not exist, you need to create it as:
CREATE DATABASE database_name;
followed by:
USE database_name;
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Using column alias in WHERE clause of MySQL query produces an error
...is
executed, the column value may not yet
be determined.
Copied from MySQL documentation
As pointed in the comments, using HAVING instead may do the work. Make sure to give a read at this WHERE vs HAVING though.
share...
What MySQL data type should be used for Latitude/Longitude with 8 decimal places?
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DECIMAL is the MySQL data-type for exact arithmetic. Unlike FLOAT its precision is fixed for any size of number, so by using it instead of FLOAT you might avoid precision errors when doing some calculations. If you were just storing and ret...