Name

The name of the table.

Engine

The storage engine for the table. See Chapter 13, Storage Engines.

Version

The version number of the table's .frm file.

Row_format

The row-storage format (Fixed, Dynamic, Compressed, Redundant, Compact). For MyISAM tables, (Dynamic corresponds to what myisamchk -dvv reports as Packed. The format of InnoDB tables is reported as Redundant or Compact. For the Barracuda file format of the InnoDB Plugin, the format may be Compressed or Dynamic.

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 tables in the INFORMATION_SCHEMA database.

Avg_row_length

The average row length.

Data_length

The length of the data file.

Max_data_length

The 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.

Index_length

The length of the index file.

Data_free

The number of allocated but unused bytes.

This information is also shown for InnoDB tables (previously, it was in the Comment value). 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 completely free 1MB 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 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:

SELECT    SUM(DATA_FREE)
    FROM  INFORMATION_SCHEMA.PARTITIONS
    WHERE TABLE_SCHEMA = 'mydb'
    AND   TABLE_NAME   = 'mytable';

For more information, see Section 20.19, “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 tablespace and the data file timestamp does not apply. For MyISAM, the data file timestamp is used; however, on Windows the timestamp is not updated by updates so the value is inaccurate.

Check_time

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

Collation

The table's character set and collation.

Checksum

The live checksum value (if any).

Create_options

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

Comment

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