3 Question about sql.-CSDN社区

I had met Itzik Ben-Gan briefl y a couple of times and knew of his reputation, so I was looking forward to his afternoon session on avoiding cursors in SQL programming at PASS. I was lucky to get there early, as the large room fi lled up quickly. Itzik took a couple of SQL programming problems and diced them up in the most skillful and entertaining way, showing the elegance and effi ciency of set-oriented thinking. The audience loved it—and so did I, except I had a different angle. Having worked on the internals of SQL Server, I could see Itzik touch the product nerves in his demos, and I admired how he turned features into beautiful solutions. After the session, I asked one of the attendees what had been his main takeaway, curious about which of the many techniques would have stood out for him. He looked at me, mildly surprised, and just said, “The man is a genius!” That pretty much sums it up. This question of cursors is more fundamental than it may appear at fi rst. It points to a deep dichotomy of tremendous practical importance. Most of us were taught to program by chopping up a task into smaller steps that, when executed in sequence, perform a desired computation. But if you approach SQL programming this way, you will get only mediocre results. Your code will be much larger and harder to maintain. It will be less effi cient, less fl exible, and less tunable. Using SQL effectively is not about an incremental extension of your procedural programming skills or about a specifi c collection of tricks. Writing SQL well requires approaching problems with a different mind-set—one that is declarative and set oriented, not procedural. This is the dichotomy. Inside Microsoft SQL Server 2008: T-SQL Querying puts together all the ingredients you need to understand this declarative and set-oriented way of thinking and become a profi cient SQL programmer, thus making an important contribution to the SQL Server development community. Its chapters on formal foundations help you understand the basis for the language philosophy and get a sense for its potential. The language itself is covered thoroughly, from the basic operations to the most advanced features, all of them explained in the context of real problem solving. The many examples show you what good SQL looks like, and they cover common patterns you are likely to fi nd when writing applications. A comprehensive chapter on query tuning explains in detail the factors that impact performance in the system, how to go about identifying issues, and how to address them effectively. Itzik assembled a strong team of collaborators to write this book. Coming from different backgrounds, all of them share a deep expertise in SQL, a passion for database technology, extensive teaching experience, and a recognized track record of contributions to the SQL Server community. Steve Kass is known for his depth of understanding and clarity of thought. Dejan Sarka contributes an extensive knowledge of the relational model and a breadth of database technologies. As for Lubor Kollar, I’ve had the pleasure of working with him on the defi nition, design, and implementation of the Query Processing engine of SQL Server for over a decade, and I deeply respect his insight. They make an outstanding team of guides who can help you improve your skills.

Pro Oracle SQL, Second Edition unlocks the power of SQL in the Oracle database—one of the most potent SQL implementations on the market today. To master it requires a multi-pronged approach: learn the language features, learn how and why the language features work, learn the supporting features that Oracle provides to help use the language effectively, and learn to think and work in sets. Table of Contents Core SQL SQL Execution Access and Join Methods SQL is About Sets It’s About the Question SQL Execution Plans Advanced Grouping Analytic Functions The Model Clause Subquery Factoring Semi-joins and Anti-joins Indexes Beyond the SELECT Transaction Processing Testing and Quality Assurance Plan Stability and Control SQL and the Optimizer Cool SQL Constructs

I had met Itzik Ben-Gan briefl y a couple of times and knew of his reputation, so I was looking forward to his afternoon session on avoiding cursors in SQL programming at PASS. I was lucky to get there early, as the large room fi lled up quickly. Itzik took a couple of SQL programming problems and diced them up in the most skillful and entertaining way, showing the elegance and effi ciency of set-oriented thinking. The audience loved it—and so did I, except I had a different angle. Having worked on the internals of SQL Server, I could see Itzik touch the product nerves in his demos, and I admired how he turned features into beautiful solutions. After the session, I asked one of the attendees what had been his main takeaway, curious about which of the many techniques would have stood out for him. He looked at me, mildly surprised, and just said, “The man is a genius!” That pretty much sums it up. This question of cursors is more fundamental than it may appear at fi rst. It points to a deep dichotomy of tremendous practical importance. Most of us were taught to program by chopping up a task into smaller steps that, when executed in sequence, perform a desired computation. But if you approach SQL programming this way, you will get only mediocre results. Your code will be much larger and harder to maintain. It will be less effi cient, less fl exible, and less tunable. Using SQL effectively is not about an incremental extension of your procedural programming skills or about a specifi c collection of tricks. Writing SQL well requires approaching problems with a different mind-set—one that is declarative and set oriented, not procedural. This is the dichotomy. Inside Microsoft SQL Server 2008: T-SQL Querying puts together all the ingredients you need to understand this declarative and set-oriented way of thinking and become a profi cient SQL programmer, thus making an important contribution to the SQL Server development community. Its chapters on formal foundations help you understand the basis for the language philosophy and get a sense for its potential. The language itself is covered thoroughly, from the basic operations to the most advanced features, all of them explained in the context of real problem solving. The many examples show you what good SQL looks like, and they cover common patterns you are likely to fi nd when writing applications. A comprehensive chapter on query tuning explains in detail the factors that impact performance in the system, how to go about identifying issues, and how to address them effectively. Itzik assembled a strong team of collaborators to write this book. Coming from different backgrounds, all of them share a deep expertise in SQL, a passion for database technology, extensive teaching experience, and a recognized track record of contributions to the SQL Server community. Steve Kass is known for his depth of understanding and clarity of thought. Dejan Sarka contributes an extensive knowledge of the relational model and a breadth of database technologies. As for Lubor Kollar, I’ve had the pleasure of working with him on the defi nition, design, and implementation of the Query Processing engine of SQL Server for over a decade, and I deeply respect his insight. They make an outstanding team of guides who can help you improve your skills.

Does Spark SQL use Hive Metastore? Ask Question Asked3 years, 3 months ago Active1 year, 5 months ago Viewed9k times 12 7 I am developing a Spark SQL application and I've got few questions: I read that Spark-SQL uses Hive metastore unde...

Caused by: java.sql.SQLException: 无效的列类型: 16 oracle，hibernate 保存数据时提示的错误。 is_deleted 默认值为 0 ，没有主动赋值给他。保存时报错。但是另外的类就没问题。但是两者的写法，一个是注解写在私有变量上，一个是写在属性上面，难道和这个有关系？测试了一下，也不行。后来经过比较发现是没有下面这两个属性，加上即可。。