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 21.31, “Extensions to SHOW Statements”.
This statement also displays information about views.
SHOW TABLE STATUS output has the
following columns:
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. 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.
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:
SELECT SUM(DATA_FREE)
FROM INFORMATION_SCHEMA.PARTITIONS
WHERE TABLE_SCHEMA = 'mydb'
AND TABLE_NAME = 'mytable';
For more information, see Section 21.12, “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).
Notes:
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
For views, all the fields displayed by
SHOW TABLE STATUS are
NULL except that Name
indicates the view name and Comment says
view.