-
Anonymous users2024-02-07Keep your eyes open.
-
Anonymous users2024-02-06Answer]: The performance optimization of the database mainly includes the following aspects: (1) whether the execution plan of the statement is normal; (2) Reduce the number of interactions between applications and data, and the execution of the same SQL statement; (3) defragmentation of database entities; (4) Reduce the association between tables, especially for batch data processing, try to query data in a single table, and unify logical processing in memory to reduce database pressure; (5) For frequently accessed data, fully benefit from database cache and application cache; (6) If the amount of data is relatively large, in the design process, in order to reduce the association with other tables, some redundant fields are added to improve the query performance.
-
Anonymous users2024-02-05Database performance optimization mainly includes the following aspects:
1. Whether the execution plan of the SQL statement is normal;
2. Reduce the number of interactions between the application and the database, and the execution of the same SQL statement;
(3) defragmentation of database entities;
(4) Reduce the association between tables, especially for batch data processing, try to query data in a single table, and unify logical processing in memory to reduce database pressure;
5. Make full use of database cache and application cache for frequently accessed data;
6. If the amount of data is relatively large, in the design process, in order to reduce the association of other tables, some redundant fields are added to improve the query performance.
In the early stage of application system development, due to the relatively small amount of data in the development database, the performance of various writing methods of SQL statements can not be realized for querying SQL statements and writing complex views, but if the application system is submitted to the actual application, with the increase of data in the database, the response speed of the system has become one of the most important problems that the current system needs to solve.
A very important aspect of system optimization is the optimization of SQL statements. For massive data, the speed difference between low-quality SQL statements and high-quality SQL statements can reach hundreds of times, which shows that for a system, it is not simply possible to realize its functions, but to write high-quality SQL statements to improve the availability of the system.
-
Anonymous users2024-02-04Answer]: B Add redundant columns Mingchang refers to adding the same column to multiple tables, which increases the burden on the database server to store the state pick, but can reduce the join operation in the query process, instead of the union operation. So choose B.
-
Anonymous users2024-02-03Answer]: B Adding redundant columns refers to adding the same column to multiple tables, so that although Zao Zheng increases the burden of database server storage, it can reduce the join operation in the process of querying and querying, instead of the union operation. So choose B.
-
Anonymous users2024-02-021. In terms of hardware, the server should not be too bad, and the read and write performance of the disk affects IO, which can be considered to use a good hard disk, such as an SSD
2. Set the parameters of the database according to the server, such as memory or something 3, when designing the table, you should choose the field type and establish the correct index 4. SQL optimization, try to use the index, do not appear full table scanning, etc., there is a lot of such information on the Internet, I will say these approximately.
-
Anonymous users2024-02-01MRR is an optimization of MySQL for specific queries. Suppose a query has a secondary index available, and after reading the secondary index, you need to return to the table to find the column values that are not on the current secondary index, because the primary key values referenced on the secondary index are not necessarily ordered, so it may cause a large number of random ios.
If you want to turn off MRR optimization, you need to set the optimizer toggle MRR to OFF.
By default, MRR will only be taken if the optimizer thinks that MRR can bring optimization, if you want to take MRR whenever you can, you need to set MRR Cost Based to OFF, but it is better not to do this, because this is really a pitfall, MRR is not necessarily good at all times, the full table scan will sometimes be faster, if you take MRR in this scenario, it will be completed.
MRR sequences the primary keys so that the subsequent operations on the disk are sequential reads instead of random reads. From the perspective of resource usage, it is to let the CPU and memory do more to exchange the sequential reads of the disk. However, sorting requires memory, and the size of this memory is controlled by the read rnd buffer size parameter.
The prospect of learning UI is good, and there are many training institutions, so the local people may choose to visit and understand the real teachers and educational strength of the school before making a choice. Share the general development of the UI, I hope it will be useful to you. >>>More
If your company is one of those CEOs who often come to see it, this design can quickly query the required information, but if you manage it yourself, I think, put"Contact"with"Correspondence units"Synthesize a table, change the field of the correspondence unit to the contact, and use SQL to quickly find it if you want to query the correspondence unit or something separately; Combine the inventory information and ** information into a table; The table on the left is pretty much the same, but there are some fields that you can adjust yourself, depending on your situation, I hope it can help
The database is generally composed of many tables, for example, the school builds a database, which can build a student table (including the student's name, age, student number, class, date of birth), a teacher table (including the teacher's name, age, teaching class, teaching category), a report sheet (including the student's student number, and the grades of each subject), etc. These are the ways in which the files are stored in the database, and try to make sure that the items in a table are closely related and have the same attributes, if this condition cannot be met, a table must be built (the redundancy of the built table has 4 levels). In order to meet the user's query needs, we also need to make a number of views, for example, you can make a view of his items have the name of the student, age, grades of each subject, and the teacher of each subject, etc., we can also export new items according to the existing items, for the purpose of simplicity, for example, the view can add an average grade, we add different permissions and roles to each view, and provide it to different people to query to protect the security of the database. >>>More
At least the basic things must be mastered, such as: the linear structure of the database, the storage method, the way to call Hezheng, and the operation of the table in the database (to use statements to erect the bench to achieve). >>>More
Database system engineers are biased towards the development, operation and management of database systems; >>>More