Analyze the key features, differences and advantages of mongodb and mysql


Mongodb and MySQL are both good databases with excellent performance. However, their success depends on the application scenario. First, we should understand their different operating environments, not just compare their advantages and disadvantages. Therefore, in this article, we will explore the key features, differences and advantages of mongodb and mysql.

After reading this article, you can have a deeper understanding of the differences between the two databases (there are great differences), so as to make the right choice.

What is MySQL?

MySQL is an open source RDBMS, that is, relational database system. More specifically, relational database system is an application program for updating, managing and designing relational database. It is very useful and conducive to program coding. Relational database is a kind of database (data is usually presented in tabular form). It supports querying data according to the association relationship between data in the same database. Mysql, PostgreSQL and SQL all belong to relational database systems, and they all have their own SQL (Structured Query Language) standards.

MySQL is one of the most commonly used open source RDBMS. It was launched in 1995 and has been highly praised by the industry for its reliability. And it is very convenient to use. Because the database schema is pre-defined according to some rules, the data exists in the form of rows and columns, and can also reflect the relationship between the fields of different tables.

What is mongodb?

Mongodb is also open source, but it is a database based on file storage, which is different from mysql. It stores documents in data sets rather than relational tables.

When using mongodb, the data pattern is not fixed. It is feasible to delete or modify some attributes of documents within a collection, which provides great flexibility. Moreover, the structure of documents in the same collection can be completely different.

Differences between mongodb and MySQL

As mentioned earlier, the main difference between the two open source databases is that MySQL is relational and mongodb is based on file storage. In this chapter, we will study what this difference represents, including data mode and capacity, performance and speed, security and query language.

Data mode and capacity

In mongodb, data exists in the form of name value pairs similar to JSON files. Due to its schema design, it has less constraints on data. Therefore, if the data changes rapidly, mongodb has great advantages. In addition, mongodb also provides a predefined structure, which can be used if necessary.

MySQL is different about data mode. Although the mode can be changed in mysql, its flexibility and dynamics are worse than those of database based on file storage. Before saving any data, MySQL will force a check. If the tables and columns meet the predefined rules after saving the data, it will be really executed. Changing the data schema also requires redesigning the DDL (data definition language) and DML (data modeling language) of the database.

Both relational database and document database use the concepts of DDL and DML. However, in relational database, the definition of DDL and DML is very important. On the contrary, mongodb’s data schema has strong scalability and does not pay attention to data structure as MySQL does. Although this seems to be a big disadvantage, this consistency is actually the biggest advantage of MySQL, because it ensures the structure of data and maintains the cleanliness of data.

Each mongodb database contains several collections or, more accurately, documents. These documents may contain a variety of information fields and types, and support the storage of data of various contents and sizes. In mysql, because the data schema is more binding and each data in a table has the same column, it is difficult to manage the database when it is large. Therefore, if the database is too large and complex, the processing capacity of MySQL is not as good as mongodb.

In other words, mongodb based on file storage is more suitable for dealing with a large number of complex data with changeable structure than relational mysql.

Performance and speed

Mongodb receives any data faster than mysql, and can receive more data than mysql. However, it is assumed that such a business has a small amount of data and less changeable data structure. Therefore, there is no need to pursue speed too much, so other characteristics (such as reliability and consistency) become the priority factors.

We need to compare the speed of each database, but it is more important to understand which database is more suitable or has better performance under the constraints of business or project requirements.

If the project needs to focus on data privacy and integrity, MySQL is a mature and reasonable solution. Because the data mode is clear, MySQL systematizes the data types with data tables, so that the respective values in the data can be fully queried and easy to search. Therefore, using MySQL means that the database structure is stable. However, it is not suitable for unstructured data. The biggest advantage (or disadvantage) of MySQL is that it needs to define the data structure in advance, which avoids a lot of technical debt. However, in some cases, the data is too complex to design an appropriate pattern.

On the other hand, mongodb is more flexible and fast in dealing with unstructured data. When the data schema is difficult to define in advance, the database based on file storage is more suitable. However, if the data is diversified, it is difficult to add an index to a certain attribute of the data. Therefore, the data model needs to be continuously optimized. At this time, if one-sided pursuit of consistency, it will bring risks.


MySQL uses a set of permission based security model, that is, the user needs identity authentication to operate the database, and the system can also grant or prohibit the user’s permission to operate a database. Moreover, if the application needs to obtain data from the database, it needs to establish an encrypted connection using SSL, a security protocol.

Mongodb’s security system is composed of role-based access control, including identity authentication, authorization and audit. In addition, TLS and SSL will also be used if encryption is required.

Although both mongodb and MySQL provide security models, which can be used when the project needs certain reliability and data consistency, MySQL is the most suitable option.

Characteristics of transactions: atomicity, consistency, isolation and persistence

In computer science, acid refers to the attributes that database transactions should have. Only when these attributes are met can the data be effective. They are atomicity, consistency, isolation and persistence.

It is generally believed that MySQL complies with the acid standard, but for mongodb, blindly meeting the acid standard is not the optimal strategy, because it will sacrifice speed and availability. Mongodb began to support acid multi document transactions in 2018. However, this option is off by default. On the other hand, MySQL transactions comply with the acid standard. In terms of transaction attributes, it can ensure data validity.


MySQL uses SQL statements to obtain data from one or more data tables. SQL is the most popular query language. It only needs to be combined with DDL and DML to communicate with the database system.

Instead, mongodb uses an unstructured query language. When querying data from a JSON based file database, the first priority is to search for documents using attributes that match the results.

In other words, in order to obtain the data in mongodb, you need to perform a query operation. This function should be executed: dB collection. find()。 Mongodb supports multiple languages (similar to python, Java, c##, Perl, PHP, ruby, and JavaScript). As long as queries can be built in this language, mongodb supports them. Compound queries can use query operators to establish specific conditions for each field in a collection document. Query operators ($and, $or, $type, $EQ, etc.) are used to define conditions and filters. The data obtained through query is determined by query conditions. Further, the objects queried, updated and deleted are determined by query conditions.

However, mongodb does not support join queries, nor does it have an equivalent alternative. MySQL supports join operators (including inner join, outer join, left join, right join and full join), which are used to obtain data from two or more tables. Simply put, these operations allow a single SQL statement to associate data in multiple tables.

Mongodb vs. MySQL: under what conditions

Because of different environments, it is difficult to say which database is better. In fact, MySQL and mongodb operate on completely different principles. They are both very useful database management systems. Therefore, even if one of them is suitable for some businesses or projects, it may not be the best choice for other different needs. The company will select the appropriate database according to different project needs.

One of the few things they have in common is open source and easy access. In addition, both systems provide commercial versions with additional functions. In addition to these similarities, the key difference between them is that one is relational and the other is not.

Mongodb is a document database. Because it does not limit the amount and type of data, it is the most suitable solution in high-capacity environment. Because mongodb has the level of scalability and flexibility required by cloud services, it is very suitable for the development of cloud computing services. In addition, it reduces the load, simplifies the expansion within the business or project, and realizes high availability and rapid data recovery.

Although mongodb has so many advantages, MySQL is also superior to mongodb in some aspects, such as reliability and data consistency. In addition, if security is a priority, MySQL is one of the most secure DBMS.

Moreover, when an application needs to treat multiple operations as one transaction (such as accounting or banking system), relational database is the most appropriate choice. In addition to security, MySQL has a high transaction rate. In fact, mongodb supports fast data insertion, while mysql, on the contrary, supports transaction operations and pays attention to transaction security.

Generally speaking, if the data mode of the project is fixed and does not need to be changed frequently, MySQL is recommended. Therefore, the project is easy to maintain and ensures the integrity and reliability of the data.

On the other hand, if the data in the project continues to increase and the data pattern is not fixed, mongodb is the most appropriate choice. Because it is a non relational database, the data can be used freely without defining a unified data structure, so it is also very convenient to update and query the data. Mongodb is usually used in projects that need to manage content, deal with Internet of things related businesses, conduct real-time analysis and other functions.


MySQL is an open source relational database, in which the data is stored in tables, and some attributes in the data can establish relationships with other tables. Mongodb is also open source, but it is a document database. Therefore, it has no concept of record and its data model is not fixed, so it is a dynamic and flexible database that can insert a large amount of data.

Before selecting the best database, the specific business requirements and project priorities should be clearly determined. As mentioned earlier, mongodb is better than MySQL in processing a large amount of data. In addition, mongodb is also true for projects with frequent changes in cloud computing services and requirements.

On the contrary, the data structure and pattern in MySQL are fixed, so the data consistency and reliability are guaranteed. Another advantage of using MySQL is that it supports transaction operations based on acid criteria and has higher data security. So for projects that value these factors, MySQL is the most appropriate.

In short, both databases can provide satisfactory performance as long as the use scenario is consistent with the requirements of the application and the characteristics of the system.