Sql Not Exists Performance

For a lot of news at home and abroad, BBS and E-commerce sites are used asp+sql design, and write ASP programmers Many (there are a lot of just graduated), so, Asp+sql attack success rate is also relatively high. This kind of attack method has little to do with the NT version and the SQL version. There is no corresponding patch, because the loophole is caused by the programmer, and most of the book on ASP programming, the source code example has this flaw exists, in fact, just some legitimate ASP on the request of SQL, leaving endless trouble! A This attack method originated from ...

We want to do not only write SQL, but also to do a good performance of the SQL, the following for the author to learn, extract, and summarized part of the information to share with you! (1) Select the most efficient table name order (valid only in the Rule-based optimizer): The ORACLE parser processes the table names in the FROM clause in Right-to-left order, and the last table in the FROM clause (the underlying table driving tables) is processed first, In the case where multiple tables are included in the FROM clause, you must select the table with the least number of records as the underlying table. If...

The logical design of database is a very broad problem. In this paper, the main key design of the table is discussed in the design of MS SQL Server, and the corresponding solutions are given. Primary key design status and problems about database table primary key design, in general, based on business requirements, based on business logic, the formation of primary key. For example, when sales to record sales, generally need two tables, one is the summary description of the sales list, records such as sales number, the total amount of a class of cases, and the other table record of each commodity ...

MySQL database sql statement commonly used optimization methods 1. Query optimization, should try to avoid full table scan, should first consider where and order by the columns involved in the establishment of the index. 2. Should be avoided in the where clause on the field null value judgment, otherwise it will cause the engine to abandon the use of indexes and full table scan, such as: select id from t where num is null You can set the default value of num 0, to ensure that Num column table does not null value ...

The establishment of enterprise security building Open source SIEM platform, SIEM (security information and event management), as the name suggests is for security information and event management system for most businesses is not cheap security system, this article combined with the author's experience describes how to use open source software Analyze data offline and use algorithms to mine unknown attacks. Recalling the system architecture to WEB server log, for example, through logstash WEB server to collect query log, near reality ...

Intermediary transaction SEO diagnose Taobao guest Cloud host technology Lobby database optimization is a very complex task, because it ultimately requires a good understanding of system optimization. 　　Even though the system or application system does not know much about the optimization effect is good, but if you want to optimize the effect of better, then you need to know more about it. 1, the optimization of the system to run faster the most important factor is the basic design of the database. 　　And you have to be aware of what your system is going to do, and the bottlenecks that exist. The most common system bottlenecks are as follows: ...

Some financial analysts questioned Teradata's ability to continue its growth in the IT market. While this segment of customers does put Hadoop on the agenda, customers often choose to give up only if data warehouse vendors with decades of experience find it difficult. "What's more important is to get rid of the misunderstanding of speculation rather than make a compromise at the level of reality," Scott Gnau, president of Teradata Labs, pointed out in a recent interview - the focus of this interview was to explore open source Hadoop from a historical perspective ...

Some financial analysts questioned Teradata's ability to continue its growth in the IT market. While this segment of customers does put Hadoop on the agenda, customers often choose to give up only if data warehouse vendors with decades of experience find it difficult. "What's more important is to get rid of the misunderstanding of speculation rather than make a compromise at the level of reality," Scott Gnau, president of Teradata Labs, pointed out in a recent interview - the focus of this interview was to explore open source Hadoop from a historical perspective ...

As an outstanding representative of the Object relational database, Oracle is undoubtedly the most powerful. Whether it's the size of the database, the support of multimedia data types, the parallelism of SQL operations replication, or the security services, Oracle is much stronger than Sybase, Informix, Added to the latest version of the Oracle8.0.4 is to enhance the characteristics of this, but also introduced a number of new features, such as: Data partitioning (partitioning), Object-relational technology (objects relational T ...

Here is a translation of the Redis Official document "A fifteen minute introduction to Redis data Types", as the title says, The purpose of this article is to allow a beginner to have an understanding of the Redis data structure through 15 minutes of simple learning. Redis is a kind of "key/value" type data distributed NoSQL database system, characterized by high-performance, persistent storage, to adapt to high concurrent application scenarios. It started late, developed rapidly, has been many ...