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Difference between natural join and inner join
... definition of a natural join is to join on *all like-named columns*. From MySQL doc: The NATURAL [LEFT] JOIN of two tables is defined to be semantically equivalent to an INNER JOIN or a LEFT JOIN with a USING clause that names all columns that exist in both tables.. And another thing - in practice ...
MySQL: Enable LOAD DATA LOCAL INFILE
I'm running Mysql 5.5 on Ubuntu 12 LTS. How should I enable LOAD DATA LOCAL INFILE in my.cnf?
18 Answers
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SQL how to make null values come last when sorting ascending
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@Martin Note this question is not tagged mysql. I provided a generalized solution - there are many different ways of doing the same thing across different dbs.
– RedFilter
Oct 16 '15 at 14:15
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How do I kill all the processes in Mysql “show processlist”?
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You need to kill them one by one, MySQL does not have any massive kill command. You can script it in any language, for example in PHP you can use something like:
$result = mysql_query("SHOW FULL PROCESSLIST");
while ($row=mysql_fetch_array($result)) {
$pro...
实战做项目如何选择开源许可协议（一）-了解协议 - 开源 & Github - 清泛网...
实战做项目如何选择开源许可协议（一）-了解协议opensource_permission目前国内开源项目正在逐渐升温，中国也开始有不少优秀的开源项目突显出来。在大家摩拳擦掌准备加入开源大军时，也要知道这个圈子里的规则。...目前国内...
mysql error 1364 Field doesn't have a default values
...does not address the root cause either because the root cause was a bug in MySQL that was fixed in v5.7.1 - see the answer by B98: stackoverflow.com/a/29854279/5389997 Removing strict_trans_table sql mode makes MySQL more prone to data quality errors, so removing it is not a really good advice.
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App Inventor 2 低功耗蓝牙(BLE) 硬件接入、数据通信及IO控制 - App Invent...
...本文主要介绍一款较为通用、价格低廉的BLE设备从零开始如何利用App Inventor 2开发一款自己专属的手机蓝牙App应用。BLE与经典蓝牙的区别可参考：《低功耗蓝牙(BLE) 和 经典蓝牙(SPP) 的区别》。本文主要通过一款常见的BLE硬件接入...
Abusing the algebra of algebraic data types - why does this work?
...gard that for the sake of simplicity.
A few initial points:
Note that "union" is probably not the best term for A+B here--that's specifically a disjoint union of the two types, because the two sides are distinguished even if their types are the same. For what it's worth, the more common term is ...
Possible to do a MySQL foreign key to one of two possible tables?
...ut logical XOR is not standard SQL and is not supported by all SQL brands. MySQL has it, but PostgreSQL does not. Oracle has it, but Microsoft does not until 2016. And so on.
– Bill Karwin
Aug 19 '15 at 15:09
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com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
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So, you have a
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
java.net.ConnectException: Connection refused
I'm quoting from this answer which also contains a step-by-step MySQL+JDBC tutorial:
If yo...