13.7.6.36 SHOW TABLE STATUS Syntax

Name

The name of the table.

Engine

The storage engine for the table. See Chapter 15, The InnoDB Storage Engine, and Chapter 16, Alternative Storage Engines.

For partitioned tables, Engine shows the name of the storage engine used by all partitions.

Version

This column is unused. With the removal of .frm files in MySQL 8.0, this column now reports a hardcoded value of 10, which is the last .frm file version used in MySQL 5.7.

Row_format

The row-storage format (Fixed, Dynamic, Compressed, Redundant, Compact). For MyISAM tables, Dynamic corresponds to what myisamchk -dvv reports as Packed.

Rows

The number of rows. Some storage engines, such as MyISAM, store the exact count. For other storage engines, such as InnoDB, this value is an approximation, and may vary from the actual value by as much as 40% to 50%. In such cases, use SELECT COUNT(*) to obtain an accurate count.

The Rows value is NULL for INFORMATION_SCHEMA tables.

For InnoDB tables, the row count is only a rough estimate used in SQL optimization. (This is also true if the InnoDB table is partitioned.)

Avg_row_length

The average row length.

Data_length

For MyISAM, Data_length is the length of the data file, in bytes.

For InnoDB, Data_length is the approximate amount of memory allocated for the clustered index, in bytes. Specifically, it is the clustered index size, in pages, multiplied by the InnoDB page size.

Refer to the notes at the end of this section for information regarding other storage engines.

Max_data_length

For MyISAM, Max_data_length is maximum length of the data file. This is the total number of bytes of data that can be stored in the table, given the data pointer size used.

Unused for InnoDB.

Refer to the notes at the end of this section for information regarding other storage engines.

Index_length

For MyISAM, Index_length is the length of the index file, in bytes.

For InnoDB, Index_length is the approximate amount of memory allocated for non-clustered indexes, in bytes. Specifically, it is the sum of non-clustered index sizes, in pages, multiplied by the InnoDB page size.

Refer to the notes at the end of this section for information regarding other storage engines.

Data_free

The number of allocated but unused bytes.

InnoDB tables report the free space of the tablespace to which the table belongs. For a table located in the shared tablespace, this is the free space of the shared tablespace. If you are using multiple tablespaces and the table has its own tablespace, the free space is for only that table. Free space means the number of bytes in completely free extents minus a safety margin. Even if free space displays as 0, it may be possible to insert rows as long as new extents need not be allocated.

For NDB Cluster, Data_free shows the space allocated on disk for, but not used by, a Disk Data table or fragment on disk. (In-memory data resource usage is reported by the Data_length column.)

For partitioned tables, this value is only an estimate and may not be absolutely correct. A more accurate method of obtaining this information in such cases is to query the INFORMATION_SCHEMA PARTITIONS table, as shown in this example:

For more information, see Section 25.17, “The INFORMATION_SCHEMA PARTITIONS Table”.

Auto_increment

The next AUTO_INCREMENT value.

Create_time

When the table was created.

Update_time

When the data file was last updated. For some storage engines, this value is NULL. For example, InnoDB stores multiple tables in its system tablespace and the data file timestamp does not apply. Even with file-per-table mode with each InnoDB table in a separate .ibd file, change buffering can delay the write to the data file, so the file modification time is different from the time of the last insert, update, or delete. For MyISAM, the data file timestamp is used; however, on Windows the timestamp is not updated by updates, so the value is inaccurate.

Update_time displays a timestamp value for the last UPDATE, INSERT, or DELETE performed on InnoDB tables that are not partitioned. For MVCC, the timestamp value reflects the COMMIT time, which is considered the last update time. Timestamps are not persisted when the server is restarted or when the table is evicted from the InnoDB data dictionary cache.

Check_time

When the table was last checked. Not all storage engines update this time, in which case, the value is always NULL.

For partitioned InnoDB tables, Check_time is always NULL.

Collation

The table default collation. The output does not explicitly list the table default character set, but the collation name begins with the character set name.

Checksum

The live checksum value, if any.

Create_options

Extra options used with CREATE TABLE. The original options from when CREATE TABLE was executed are retained and the options reported here may differ from the active table settings and options.

For InnoDB tables, the actual ROW_FORMAT and KEY_BLOCK_SIZE options are reported. Prior to MySQL 8.0, Create_options reports the originally supplied ROW_FORMAT and KEY_BLOCK_SIZE. For more information, see Section 13.1.20, “CREATE TABLE Syntax”.

Create_options shows partitioned if the table is partitioned. It also shows the ENCRYPTION option specified when creating or altering a file-per-table tablespace. This column does not show the encryption option specified when creating or altering a general tablespace. The ENCRYPTION column of the INNODB_TABLESPACES table is applicable to both file-per-table and general tablespaces.

Comment

The comment used when creating the table (or information as to why MySQL could not access the table information).

For NDB tables, the output of this statement shows appropriate values for the Avg_row_length and Data_length columns, with the exception that BLOB columns are not taken into account.

For NDB tables, Data_length includes data stored in main memory only; the Max_data_length and Data_free columns apply to Disk Data.

For NDB Cluster Disk Data tables, Max_data_length shows the space allocated for the disk part of a Disk Data table or fragment. (In-memory data resource usage is reported by the Data_length column.)

For MEMORY tables, the Data_length, Max_data_length, and Index_length values approximate the actual amount of allocated memory. The allocation algorithm reserves memory in large amounts to reduce the number of allocation operations.

For views, most columns displayed by SHOW TABLE STATUS are 0 or NULL except that Name indicates the view name, Create_time indicates the creation time, and Comment says VIEW.