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01. Technical characteristics of MySQL?

Mysql database software is a client or cloud server system that supports multithreaded SQL cloud servers with various client programs and libraries, different backends, extensive application programming interfaces and management tools

02. MySQL default port number?

3306

03. What are the advantages of MySQL

MySQL is open source software, ready to use, free of charge. Provides management tools for managing, checking and optimizing database operations, GUI with command prompt, supports multiple storage engines, and supports multithreading to make full use of CPU resources

04. What are the storage engines supported by MySQL and their features?

MySQL5.7 support: InnoDB, MyISAM, MERGE, MEMORY, ARCHIVE, CSV, PERFORMANCE_SCHEMA, BLACKHOLE

InnoDB is the default transactional engine of MySQL. It is the most important and widely used storage engine. It supports transaction security tables, row locking and foreign keys.

MyISAM is based on ISAM storage engine and extends it. MyISAM has high insertion and query speed, but does not support things and foreign keys.

The MERGE storage engine is a combination of a set of MyISAM tables, and the MyISAM table structure must be exactly the same

The MEMORY storage engine stores the data in the table in memory, and provides fast access without querying and referencing other table data.

PERFORMANCE_SCHEMA engine is mainly used to collect performance parameters of database cloud servers.

05. How to check the MySQL version?

SELECT VERSION ()

06, the difference between char and varchar?

The length of the CHAR column is fixed to the length declared when the table is created, and the length values range from 1 to 255. when Char values are stored, they are filled with spaces to a specific length, and trailing spaces need to be removed when retrieving Char values.

The length of the VARCHAR column can be changed to the length declared when the table is created, and when the VARCHAR value is stored, the length can be automatically changed (can be reduced).

07. What is the meaning of% and _ in fuzzy query like?

% represents 0 or more characters, and _ represents 1 character.

08. Is the MySQL query case sensitive?

MySQL is not case sensitive

09. How to query the first 50 records in MySQL?

SELECT * FROM table name LIMIT 0pl 50

10. What's the difference between NOW () and CURRENT_DATE ()?

The NOW () command is used to display the current year\ month\ day\ hours\ minutes\ seconds

CURRENT_DATE () displays only the current year\ month\ day

11. What is InnoDB?

InnoDB is one of the database engines of MySQL and is now the default storage engine for MySQL. InnoDB, developed by Innobase Oy, supports ACID-compatible transaction functions.

12. What happens if the maximum value is reached in the table when the column is set to AUTO INCREMENT?

Stop incrementing, any further insertion will result in an error

13. How do you view all the indexes defined in the table?

SHOW INDEX FROM table name\ G

14. What will happen if a table has a column defined as TIMESTAMP

Whenever a row is changed, the timestamp field gets the current timestamp.

15. How to distinguish between FLOAT and DOUBLE?

Floating-point numbers are stored in FLOAT with 8-bit precision and have four bytes, while floating-point numbers are stored in DOUBLE with 18-bit precision and have eight bytes

16. How many TRIGGERS are allowed in the MySQL table?

17. What's the difference between LIKE and REGEXP operations?

LIKE matches the entire column, and if the matched text appears in the column value, LIKE will not find it and the corresponding row will not be returned (no wildcards are used)

REGEXP matches within the column value, and if the matched text appears in the column value, REGEXP will find it and the corresponding row will be returned.

18. What is the difference between CHAR_LENGTH and LENGTH functions?

CHAR_LENGTH is the number of characters, while LENGTH is the number of bytes. The two data of Latin characters are the same, but they are different for Unicode and other encodings.

19. What is the statement to import / export database data?

Import-- > mysql-u username-p password database name

Mysqldump-u user name-p database name > exported file name

20. There is an ID self-increasing primary key in a table. When insert has 17 records, delete 15, 16 and 17 records, restart MySQL, and then insert a record. Is the ID of this record 18 or 15?

If the type of the table is InnoDB, 15

If the table is of type MyISAM, it is 18.

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