由于自己开发环境使用的是MS SQLServer 2005,而服务器上部署的依然是MS SQLServer 2000,于是在系统开发完成后,还得将MS SQLServer 2005导入 MS SQLServer 2000,虽然同是MS家族的产品,导入导出也算方便,但是有时候也会出现问题,比喻说这样操作: 1、在
由于自己开发环境使用的是MS SQLServer 2005,而服务器上部署的依然是MS SQLServer 2000,于是在系统开发完成后,还得将MS SQLServer 2005导入 MS SQLServer 2000,虽然同是MS家族的产品,导入导出也算方便,但是有时候也会出现问题,比喻说这样操作:
1、在SQL Server Management Studio中,选择数据,生成脚本
2、选择下一步,然后在“为服务器版本编写脚本”选择SQL Server 2000
3、下一步选择要生成的表或者视图,最后完成,然后将生成的脚本复制到SQL Server 2000下执行。
从上面的流程来看,并没有什么问题,但是在执行的过程中却无法执行,需要将脚本中做如下调整:
找到"WITH (IGNORE_DUP_KEY = OFF) ON "这一句,,用全部替代为空
找到"sys.objects",用全部替代为"sysobjects"
找到"sys.views",用全部替代为"sysobjects"
找到"object_id",用全部替代为"id"[注:这里的object_id要区分大小写]
找到"sys.sp_addextendedproperty",用全部替代为"dbo.sp_addextendedproperty"或是"sp_addextendedproperty"
找到"EXEC sys.sp_addextendedproperty @name=N''XXX'', @value=N''XXX'' , @level0type=N''SCHEMA'', @level0name=N''XXX'', @level1type=N''XXX'', @level1name =N''XXX''"这一句,将@level0type=N''SCHEMA''改成@level0type=N''user'',再把@name=,@value =,@level0type=,@level0name=,@level1type=,@level1name=全部替代为空
如果在生成脚本的时候,将“为所选数据库中的所有对象编写脚本”选中,其他步骤一切照旧,则可以生成完全正常的脚本,不需要修改任何地方。

InnoDB 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.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary 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

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.


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