How to query data size in MySQL

MySQL is a commonly used relational database management system (RDBMS). It has a variety of functions, among which query is one of the core functions. MySQL can not only store massive amounts of data, but also support various types of queries to meet the different needs of users. When querying data, sometimes you need to obtain the size information of the data. This article will introduce how to query the data size in MySQL.

1. Use the SUM function to query the data size

In MySQL, you can use the SUM function to query the sum of a field in the data table. By calculating the sum of the data in the data table field, the data size of the field can be obtained. The following is an example:

SELECT SUM(LENGTH(column_name)) FROM table_name;

Among them, column_name is the name of the field in the data table whose size needs to be calculated, and table_name is the name of the data table. In the query results, the sum of the sizes of the queried fields will be returned. For example, if you query the total size of a field in a data table, you can use the following code:

SELECT SUM(LENGTH(content)) FROM article;

2. Use the DATA_LENGTH function to query the data size

Use MySQL The DATA_LENGTH function can also query the size of a data table. The function of this function is to obtain the size of the disk space occupied by the data table. The following is how to use the DATA_LENGTH function:

SELECT DATA_LENGTH FROM information_schema.TABLES WHERE TABLE_NAME = 'table_name';

Among them, table_name is the name of the data table you want to query. In the query results, the size of the queried data table will be returned. For example, if you query the size of a data table article, you can use the following code:

SELECT DATA_LENGTH FROM information_schema.TABLES WHERE TABLE_NAME = 'article';

3. Use the LENGTH function to query the data size

You can also use the LENGTH function in MySQL Easily query the size of data, it calculates the length of a string. However, for BLOB and TEXT type fields, it will return the size of the space they occupy rather than the size of the stored data. The following is how to use the LENGTH function:

SELECT LENGTH(column_name) FROM table_name;

Among them, column_name is the name of the field whose data size needs to be queried, and table_name is the name of the data table. For example, if you query the size of a field in a data table article, you can use the following code:

SELECT LENGTH(content) FROM article;

Through the above three methods, you can easily query the data size in MySQL. Different methods will provide better query results in different scenarios, so choosing the most suitable method can get better query results.

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