What is the subject of the database
The main body of the database is a collection of all business data required by related applications, which is called a physical database. A database is a collection of organized, shareable, and unified management of large amounts of data stored in a computer for a long time. The main body of the database is a collection of all business data required by related applications, which is called a physical database. (Learning video recommendation: mysql video tutorial) Related knowledge introduction: Database is “a warehouse that organizes, stores and manages data according to the data structure” . It is a collection of large amounts of data that is stored in a computer for a long time, organized, shareable, and managed in a unified manner. A database is a warehouse for storing data. It has a large storage space and can store millions, tens of millions, or hundreds of millions of data. But the database does not store data randomly, there are certain rules, otherwise the query efficiency will be very low. Today’s world is an Internet world full of data, filled with a lot of data. That is, the Internet world is the data world. There are many sources of data, such…
How does mysql query a row of data in a table
Mysql query method for a row of data in the table: use the select statement to query, use the where condition to select by row, the syntax is [select * from where ]. The method of mysql querying a row of data in the table: The basic syntax of the Select statement: p> Select from where order by if To query all the data of a specified row in a table, the query statement can be written as: select * from where Why is this statement, a brief analysis. So the data actually includes all the rows and all the columns, so: 1. First select all the columns The “column set” should include all field. An asterisk (*) can be used in SQL statements to refer to all fields. 2. Then select the specified row Use the where condition to select by row. Let’s look at an example to query all records in the test table whose t_name value is name2: mysql> select * from test where t_name='name2'; +——+——–+——————————— -+————+ |t_id|t_name|t_password|t_birth| +——+——–+——————————— -+————+ | 2 | name2 | 12345678901234567890123456789012 | 2013-01-01 | +——+——–+——————————— -+————+ 1 rows in set (0.00 sec) More related free learning recommendation: mysql tutorial (video) The above…
How to configure mysql after installing
mysql php Write your review! Let’s make a fuss, see everything Member Login | User Registration recommended reading bash How to check the reason why the docker container stopped O&M|Docker view,docker,stop,reason O&M-Dockerdocker container service stopHow to troubleshoot errors? During the use of the container, if the service is unavailable, it is necessary to troubleshoot the errors in the container and fix the … [detailed] Crayon Shinchan 2023-08-26 13:03:05 bash MySQL function to obtain the current time of the system [MySQL] Database | mysql tutorial time, system database-mysql tutorial bitsCN.comMySQL function to get the current time of the system Environment: MySQLServer5.1 Question: The function of MySQL to get the current time of the system … [detailed] Crayon Shinchan 2023-08-26 13:03:19
What is the role of database index
The purpose of a database index is to provide quick access to specific information in a database table. Indexes can improve the speed of data search and retrieval, can speed up the connection speed between tables, and can also improve the efficiency of the server in processing related search requests. Building an index can greatly improve the speed of obtaining the required information in the database, and at the same time improve the efficiency of the server in processing related search requests. From this aspect It has the following advantages: When designing a database, by creating a unique index, a one-to-one mapping relationship can be formed between the index and the information, increasing the uniqueness of the data . It can improve the speed of data search and retrieval, which is in line with the original intention of database establishment. It can speed up the connection speed between tables, which plays an important role in improving the referential integrity of data. In the information retrieval process, if the grouping and sorting clauses are used, the indexing can effectively reduce the grouping and sorting time required in the retrieval process and improve retrieval efficiency. After the index is established, the optimization…
What phase of database design does index design belong to?
Index design belongs to the physical design phase of database design. Database design refers to the construction of an optimal database model for a given application environment, the establishment of a database and its application system, so that it can store data effectively and meet the application needs of various users. Index design belongs to the physical design phase of database design. (Learning video sharing: mysql video tutorial) Complete the data flow diagram and data dictionary in the requirement analysis stage; complete the E-R diagram design in the conceptual design stage; complete the relational model design and View design; physical design determines the storage structure of data and designs indexes to improve query efficiency. Database design refers to constructing an optimal database schema for a given application environment, establishing a database and its application system so that it can store data effectively and meet the application needs of various users (information requirements and processing requirements). In the field of databases, various systems that use databases are often collectively referred to as database application systems. The design content of database design includes: requirement analysis, conceptual structure design, logical structure design, physical structure design, database implementation and database operation and maintenance.
What is droptable command?
drop table is a command used to delete one or more data tables in the database, the specific format is “DROP TABLE [IF EXISTS] table name list”; if you want to delete multiple tables at the same time, just put the table name Write them one after the other, separated by commas. View data tables mysql> SHOW TABLES; +——————–+ |Tables_in_test_db| +——————–+ |tb_emp1| |tb_emp2| |tb_emp3| +——————–+ 3 rows in set (0.00 sec) It can be seen from the running results that there are three data tables tb_emp1, tb_emp2 and tb_emp3 in the test_tb database. Let’s delete the data table tb_emp3, the entered SQL statement and the running results are as follows: mysql> DROP TABLE tb_emp3; Query OK, 0 rows affected (0.22 sec) mysql> SHOW TABLES; +——————–+ |Tables_in_test_db| +——————–+ |tb_emp1| |tb_emp2| +——————–+ 2 rows in set (0.00 sec) For more programming knowledge, please visit: Programming Video! ! The above is what command is drop table? For more details, please pay attention to other related articles on 1024programmer.com!
What is the difference between a relational database and a non-relational database?
Difference: Relational data is naturally in table format, so it is stored in the rows and columns of the data table; data tables can be associated with each other and stored collaboratively, and it is easy to extract data. Non-relational data is not suitable for storage in rows and columns of data tables, but is combined in large chunks; non-relational data is usually stored in datasets, like documents, key-value pairs, or graph structures. For more programming knowledge, please visit: Programming Video Course! ! The above are the differences between relational databases and non-relational databases? For more details, please pay attention to other related articles on 1024programmer.com!
Selection of binlog format when using binlog in MySQL
The mysql tutorial column introduces the selection of binlog format when using binlog. 1. Three modes of binlog 1.statement level Mode Every sql that modifies data will be recorded in the bin-log of the master. When the slave is replicating, the sql process will be parsed into the same sql that was executed on the original master side to execute again. Advantages: The advantages of the statement level are firstly to solve the shortcomings of the row level. It does not need to record the changes of each row of data, reduce the amount of bin-log logs, save io, and improve performance. Because he only needs to record the details of the statement executed on the master, as well as the context information when executing the statement. Disadvantages: Since it is a recorded execution statement, in order to make these statements execute correctly on the slave side, it must also record some relevant information when each statement is executed, that is, context information, to ensure that all statements are in When the slave side is executed, it can get the same result as when it is executed on the master side. In addition, due to the rapid development of mysql…
Is the join function of MySQL weak?
Today’s mysql tutorial column introduces the join function. About the join of MySQL, you must know a lot of its “anecdotes and anecdotes”. For example, the join of two tables requires a small table to drive a large table. The join operation on the table, the join function of MySQL is weak and so on. These norms or remarks are either true or false, sometimes right and sometimes wrong, and you need to have a deep understanding of join to understand clearly. Next, let’s take a comprehensive look at the join operation of MySQL. text In daily database query, we often have to perform table linking operations on multiple tables to obtain the merged results of multiple tables at one time Data, this is the join syntax to use the database. join is a very common operation in the data field to merge two datasets. If you know more about it, you will find that MySQL, Oracle, PostgreSQL and Spark all support this operation. The protagonist of this article is MySQL. If there is no special explanation below, the join of MySQL is the subject. On the other hand, Oracle, PostgreSQL and Spark can be regarded as the big bosses…
How to open a file in mysql
How to open files in mysql: first open “My Computer->Properties->Advanced System Settings->Environment Variables” in sequence; then find the path; then add the bin directory under the mysql address on the computer ; Finally, open cmd and enter the sql command to view the file. Recommendation: “Mysql Video Tutorial” Open the file with the mysql command line First of all, you need to configure system variables, go to My Computer->Properties->Advanced System Settings->Environment Variables->find the path, and add the bin directory under the mysql address on your computer, such as c:/wampp/mysql/bin : Open cmd and enter the following command (no need to convert directory) > mysql -u root -p enter password: After entering mysql mysql>use test; mysql> source c:/test.sql ok is finished You can use show tables; to check which tables are written (remember there is a semicolon after the statement) You can also use desc tablename; to view your table structure The above is the detailed content of how to open the file in mysql, please pay attention to other related articles on 1024programmer.com for more!
