每个人都会犯错误，但作为数据库管理员，我们应该尽量避免失误，从而为公司降低成本，并确保数据质量。下面的五个数据库设计失误必须引起我们的警惕。
1.选择恰当的数据类型，避免数据库的过度膨胀
请留意数据类型的选择。例如，如果你很清楚某列的数值范围在0-100,000之间，那么就不必使用BIGINT数据类型，因为INT类型就已经足够了。
选择前者意味着，你每插入一条数据就比后者浪费了4个字节。这听起来也许微不足道，但随着数据量的增长，问题将会凸显出来。
2.遵循ISO标准，保证异构数据库系统之间的互通性
大型企业的IT基础架构非常复杂，可能需要不同数据库系统之间的数据交换。我们以TIMESTAMP数据类型为例，在Transact-SQL中定义的TIMESTAMP数据类型与ISO标准有所不同。其它的数据库系统与ISO标准也有所差别。所以，我们要尽可能地遵循ISO标准，以保证异构数据库系统之间的互通性。
3.以恰当的机制实现序列化
保证在数据库中插入记录的序列化非常有必要，许多数据库设计者通过各种机制来确保序列化的应用。一些数据库设计者喜欢在数据库设计中引入GUID，但引入GUID并不是一个好的选择，这是因为GUID默认并非序列化的，使用GUID列作为主键和/或索引甚至会造成性能问题。
4.创建索引时要将外键考虑在内
如果你的数据库中已定义外键，那么在建立索引的时候就要多加留神了，要把这种情况纳入数据库设计的整体之中去。
5.不要忽略与业务需求相关的候选键
数据库设计者不应只将注意力放在代理键上，而忘却业务需求。显然，这对数据质量非常不利。如果你没有在与业务相关的候选键上建立任何约束或索引，可能会出现重复值。
请远离上面的5个数据库设计失误吧，这会帮助你为公司节省成本，并提高数据质量。
原文链接：Do You Make These 5 Database Design Mistakes?
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Explain the role of InnoDB redo logs and undo logs.Apr 15, 2025 am 12:16 AMInnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.
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What is the Using temporary status in EXPLAIN and how to avoid it?Apr 15, 2025 am 12:14 AMUsingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB
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