How do you determine the actual size of a MySQL database?

Determining the True Size of a MySQL Database

To ascertain the storage space occupied by a MySQL database, a common misconception arises in interpreting the output of the SHOW TABLE STATUS LIKE 'table_name' command. While the Data_Length parameter displays the number of data bytes in a specific table, it does not account for the total data size across the entire database.

To accurately determine the database size, a comprehensive query is required that considers all tables and their associated data and index lengths. The following SQL statement provides the desired results:

<code class="sql">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;</code>

Index Length Explanation

The Index Length value in the SHOW TABLE STATUS output refers to the storage space allocated to index structures for the specified table. Indexes enhance query performance by organizing table data efficiently, but they also contribute to the overall database size. Understanding the index length is crucial when optimizing storage space and ensuring optimal query speeds.

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