SHOW TABLE STATUS [{FROM | IN} db_name]
[LIKE 'pattern' | WHERE expr]
SHOW TABLE STATUS works likes
SHOW TABLES, but provides a lot
of information about each non-TEMPORARY
table. You can also get this list using the mysqlshow
--status db_name command.
The LIKE clause, if present,
indicates which table names to match. The
WHERE clause can be given to select rows
using more general conditions, as discussed in
Section 20.27, “Extensions to SHOW Statements”.
This statement also displays information about views.
SHOW TABLE STATUS returns the
following fields:
Name
The name of the table.
Engine
The storage engine for the table. See Chapter 14, 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.
Beginning with MySQL 5.1.24, 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 20.11, “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).
Before MySQL 5.1.24, free space for
InnoDB tables is reported in the comment.
As of 5.1.24, it is reported in the
Data_free 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 NDBCLUSTER 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. Prior to MySQL 5.1.21, the number of MySQL Cluster
replicas was shown in the Comment column as
number_of_replicas (Bug #11379).
For views, all the fields displayed by SHOW
TABLE STATUS are NULL except that
Name indicates the view name and
Comment says view.