show table status
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
). ForMyISAM
tables, (Dynamic
corresponds to what myisamchk -dvv reports asPacked
. The format ofInnoDB
tables is reported asRedundant
orCompact
. For theBarracuda
file format of theInnoDB Plugin
, the format may beCompressed
orDynamic
.Rows
The number of rows. Some storage engines, such as
MyISAM
, store the exact count. For other storage engines, such asInnoDB
, this value is an approximation, and may vary from the actual value by as much as 40 to 50%. In such cases, useSELECT COUNT(*)
to obtain an accurate count.The
Rows
value isNULL
for tables in theINFORMATION_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 theComment
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 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 eachInnoDB
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. ForMyISAM
, 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 whenCREATE 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 NDBCLUSTER
tables, the output of this statement shows appropriate values for the Avg_row_length
andData_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 andComment
says view
.
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