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Updating MySQL primary key
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Insert into a MySQL table or update if exists
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Check out REPLACE
http://dev.mysql.com/doc/refman/5.0/en/replace.html
REPLACE into table (id, name, age) values(1, "A", 19)
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Unioning two tables with different number of columns
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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...cally, a lot of dbms have been quite poor when it comes to handling joins (MySQL being a particularly noteworthy example). So n+1 has, often, been notably faster than a join. And then there are ways to improve on n+1 but still without needing a join, which is what the original problem relates to.
H...
How can I do an UPDATE statement with JOIN in SQL Server?
...Here are some ways to do it in ANSI/ISO (aka should work on any SQL DBMS), MySQL, SQL Server, and Oracle. Be advised that my suggested ANSI/ISO method will typically be much slower than the other two methods, but if you're using a SQL DBMS other than MySQL, SQL Server, or Oracle, then it may be the ...
How to change the foreign key referential action? (behavior)
...re
Example:
I have a UserDetails table refers to Users table:
mysql> SHOW CREATE TABLE UserDetails;
:
:
`User_id` int(11) DEFAULT NULL,
PRIMARY KEY (`Detail_id`),
KEY `FK_User_id` (`User_id`),
CONSTRAINT `FK_User_id` FOREIGN KEY (`User_id`) REFERENCES `Users` (`User_id`)
:
:
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MySQL IF NOT NULL, then display 1, else display 0
... NOT NULL) AS addressexists
This works because TRUE is displayed as 1 in MySQL and FALSE as 0.
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mysql - how many columns is too many?
...tables with many rows, modifying the indexes can take a very long time, as MySQL needs to rebuild all of the indexes in the table. Having the indexes split over several table could make that faster.
Depending on your queries and column types, MySQL could be writing temporary tables (used in more co...
ZMQ: 基本原理 - 开源 & Github - 清泛网 - 专注C++内核技术
...的一个。 本文的目的是解释ØMQ架构的基本概念，它们是如何组合起来的，以及它们被如此设计的原因。 拓扑 拓扑是ØMQ最主要的概念，除非你知道“拓扑”代表什么，否则将与其他概念混淆更难理解，甚至理解不当。 按...