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MySQL JOIN the most recent row only?
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For anyone who must work with an older version of MySQL (pre-5.0 ish) you are unable to do sub-queries for this type of query. Here is the solution I was able to do and it seemed to work great.
SELECT MAX(d.id), d2.*, CONCAT(title,' ',forename,' ',surname) AS name
FROM cust...
MQTT与TCP的区别 - 创客硬件开发 - 清泛IT社区，为创新赋能！
... Maori dictionary)。10. mqtt客户端connect时，可以带有用户名和密码，用于验证客户端。服务端可以根据clientid、IP地址、用户名等进行ACL访问控制。可以通过自定义应用消息实现客户端对服务端的身份验证。11. 有商业和开源的mqtt broke...
How do I check if an index exists on a table field in MySQL?
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Use SHOW INDEX like so:
SHOW INDEX FROM [tablename]
Docs: https://dev.mysql.com/doc/refman/5.0/en/show-index.html
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Windows: XAMPP vs WampServer vs EasyPHP vs alternative [closed]
...o, but I want to open it up further to include all possible Windows/Apache/MySQL/PHP stacks.
5 Answers
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Is it possible to roll back CREATE TABLE and ALTER TABLE statements in major SQL databases?
...tive.
Is DDL transactional according to this document?
PostgreSQL - yes
MySQL - no; DDL causes an implicit commit
Oracle Database 11g Release 2 and above - by default, no, but an alternative called edition-based redefinition exists
Older versions of Oracle - no; DDL causes an implicit commit
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MySQL CONCAT returns NULL if any field contain NULL
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mysql has IFNULL(arg, default) instead COALESCE with the same syntax
– Vasilii Suricov
Feb 19 '19 at 17:58
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How to get next/previous record in MySQL?
...ding that a primary key colum is not meant as a column to sort by, because MySQL does not guarantee that higher, auto incremented, values are necessarily added at a later time.
If you don't care about this, and simply need the record with a higher (or lower) id then this will suffice. Just don't us...
Joining three tables using MySQL
I have three tables named
8 Answers
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BIO与NIO、AIO的区别(这个容易理解) - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...给OS处理，需要将数据缓冲区地址和大小传给OS(银行卡和密码)，OS需要支持异步IO操作API）；
阻塞 ： ATM排队取款，你只能等待（使用阻塞IO时，Java调用会一直阻塞到读写完成才返回）；
非阻塞 ： 柜台取款，取个号，然后坐在...
How to delete from select in MySQL?
This code doesn't work for MySQL 5.0, how to re-write it to make it work
4 Answers
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