Name

The name of the table.

Engine

The storage engine for the table. See Chapter 15, Alternative 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. InnoDB table format is either Redundant or Compact when using the Antelope file format, or Compressed or Dynamic when using the Barracuda file format.

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.

Refer to the notes at the end of this section for related information.

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.

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 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 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:

				
				
				
				
     
     

					
					
      
      

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

For more information, see Section 21.13, “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.

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).

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 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 views, all the fields displayed by SHOW TABLE STATUS are NULL except that Name indicates the view name and Comment says view.