How to Calculate the True Size of a MySQL Database and Avoid Misleading Statistics?

Calculating the True Size of a MySQL Database

Determining the accurate storage requirements of a MySQL database is crucial for selecting a suitable web host. The following guide explores the intricacies of this task and provides a solution to obtain the actual database size.

Understanding the Data Rows

The SHOW TABLE STATUS LIKE 'table_name' command provides information about a specific table. The Data_Length column represents the total length of all data rows in that table. However, this value may be misleading due to row padding and empty column values.

The True Data Size

The true data size is calculated by multiplying the average row length with the number of rows in the table. In your example, the table contains 400 rows with an average row length of 55 bytes. Therefore, the true data size for this table is 400 * 55 = 22,000 bytes, not 362,000 bytes.

Index Length

The Index Length column indicates the space occupied by indexes associated with the table. Indexes are data structures that speed up query execution by providing a faster lookup mechanism. The size of indexes depends on various factors, such as the number of indexes created, their size, and the data distribution.

Calculating the Database Size

To obtain the total size of a MySQL database, you can use the following query:

SELECT table_schema "database name",
    sum( data_length + index_length ) / 1024 / 1024 "database size in MB",
    sum( data_free )/ 1024 / 1024 "free space in MB"
FROM information_schema.TABLES
GROUP BY table_schema;

This query retrieves the database name, database size in megabytes, and free space in megabytes for all databases on the server. This information will assist you in determining the appropriate web hosting plan for your database needs.

The above is the detailed content of How to Calculate the True Size of a MySQL Database and Avoid Misleading Statistics?. For more information, please follow other related articles on the PHP Chinese website!