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领域驱动设计系列（二）:领域Model？ - 更多技术 - 清泛网 - 专注C/C++及内核技术
...易让大家搞糊涂。 我觉得先抛开这些概念，后面再来说如何设计聚合，先简单来说。
模型
过去，我们在多层设计里定义了很多Model, 数据库的Model(DB Entity), 然后为了不依赖数据库，我们有设计了业务的Domain Model, 同时我们又设...
How to debug PDO database queries?
...ments to Rails, but that the benefit is much heavier in PostgreSQL than in MySQL. He said that this is because MySQL doesn't actually create the query plan until you execute the prepared query.
– Nathan Long
Jul 20 '11 at 13:46
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How do I check to see if a value is an integer in MySQL?
I see that within MySQL there are Cast() and Convert() functions to create integers from values, but is there any way to check to see if a value is an integer? Something like is_int() in PHP is what I am looking for.
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Importance of varchar length in MySQL table
I have a MySQL table where rows are inserted dynamically. Because I can not be certain of the length of strings and do not want them cut off, I make them varchar(200) which is generally much bigger than I need. Is there a big performance hit in giving a varchar field much more length than necessar...
How to subtract 30 days from the current datetime in mysql?
How do I subtract 30 days from the current datetime in mysql?
8 Answers
8
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Are duplicate keys allowed in the definition of binary search trees?
...a BST which allows either of the right or left children to be equal to the root node, will require extra computational steps to finish a search where duplicate nodes are allowed.
It is best to utilize a list at the node to store duplicates, as inserting an '=' value to one side of a node requires r...
Maximum length of a table name in MySQL
What is the maximum length of a table name in MySQL?
4 Answers
4
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How to delete a column from a table in MySQL
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Here's a working example.
Note that the COLUMN keyword is optional, as MySQL will accept just DROP IsDeleted. Also, to drop multiple columns, you have to separate them by commas and include the DROP for each one.
ALTER TABLE tbl_Country
DROP COLUMN IsDeleted,
DROP COLUMN CountryName;
This...
Mysql substr和Oracle substr区别 - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
Mysql substr和Oracle substr区别Oracle substr(字符串，开始索引、从0起，长度)Mysql substr或substring(字符串，开始索引、从1起，长度)Oracle substr(字符串，开始索引、从0起，长度)
Mysql substr或substring(字符串，开始索引、从1起，长度)Mysql Orac...
mysql实现split分割字符串（length, SUBSTRING_INDEX, substring） - 数据...
mysql实现split分割字符串（length, SUBSTRING_INDEX, substring）由于MySql没有直接的split函数，只提供了length, SUBSTRING_INDEX, substring三个函数，这里介绍如何用这三个函数实现split功能。# SUBS...由于MySql没有直接的split函数，只提供了length, SUB...