MySQL之SHOW TABLE STATUS命令-白红宇

MySQL之SHOW TABLE STATUS命令

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13.7.5.37 SHOW TABLE STATUS Syntax

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SHOW

TABLE

STATUS

[{

FROM

IN}

db_name

]

[

'pattern'

WHERE

expr

]

works likes , but provides a lot of information about each non-TEMPORARY table. You can also get this list using the command. The 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 .

This statement also displays information about views.

output has the following columns:

Name

The name of the table.

Engine

The storage engine for the table. See .

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 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 .

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 and the data file timestamp does not apply. Even with mode with each InnoDB table in a separate .ibd file, 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 . The original options supplied when 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 tables, the output of this statement shows appropriate values for the Avg_row_length and Data_length columns, with the exception that columns are not taken into account

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

[FROM db_name] 可选，表示查询哪个数据库下面的表信息。

[LIKE 'pattern'] 可选，表示查询哪些具体的表名。

2、例如

(1)、show table status from db_name

查询db_name 数据库里所有表的信息

(2)、show table status from db_name like 'esf_seller_history'\G;

查询db_name 里 esf_seller_history 表的信息

(3)、show table status from db_name LIKE 'uc%'

查询db_name 数据库里表名以uc开头的表的信息

show table status 获取表的信息

show table status like 'tableName' \G

1.Name

表名称

2.Engine:

表的存储引擎

3.Version:

版本

4.Row_format

行格式。对于MyISAM引擎，这可能是Dynamic，Fixed或Compressed。动态行的行长度可变，例如Varchar或Blob类型字段。固定行是指行长度不变，例如Char和Integer类型字段。

5. Rows

表中的行数。对于非事务性表，这个值是精确的，对于事务性引擎，这个值通常是估算的。

6.Avg_row_length

平均每行包括的字节数

7.Data_length

整个表的数据量(单位：字节)

8.Max_data_length

表可以容纳的最大数据量

9.Index_length

索引占用磁盘的空间大小

10.Data_free

对于MyISAM引擎，标识已分配，但现在未使用的空间，并且包含了已被删除行的空间。

11.Auto_increment

下一个Auto_increment的值

12.Create_time

表的创建时间

13.Update_time

表的最近更新时间

14.Check_time

使用 check table 或myisamchk工具检查表的最近时间

15.Collation

表的默认字符集和字符排序规则

16.Checksum

如果启用，则对整个表的内容计算时的校验和

17.Create_options

指表创建时的其他所有选项

18.Comment

包含了其他额外信息，对于MyISAM引擎，包含了注释徐标新，如果表使用的是innodb引擎，将现实表的剩余空间。如果是一个视图，注释里面包含了VIEW字样。

 SHOW TABLE STATUS会返回以下字段： 
               Name 
         表的名称 
       
         Engine 
         表的存储引擎。在MySQL 4.1.2之前，本值被标记为Type。 
       
         Version 
         表的.frm文件的版本号 
       
         Row_format 
         行存储格式（Fixed, Dynamic, Compressed, Redundant, Compact）。InnoDB表的格式被报告为Redundant或Compact 
       
         Rows 
         行的数目。部分存储引擎，如MyISAM，存储精确的数目。对于其它存储引擎，比如InnoDB，本值是一个大约的数，与实际值相差可达40到50％。在这些情况下，使用SELECT COUNT(*)来获得准确的数目。对于在INFORMATION_SCHEMA数据库中的表，Rows值为NULL。 
       
         Avg_row_length 
         平均的行长度。 
   
       
         Data_length 
         数据文件的长度。 
       
         Max_data_length 
         数据文件的最大长度。如果给定了数据指针的大小，这是可以被存储在表中的数据的字节总数。 
   
       
         Index_length 
         索引文件的长度。 
       
         Data_free 
         被整序，但是未使用的字节的数目。 
       
         Auto_increment 
         下一个AUTO_INCREMENT值。 
       
         Create_time 
         表创建时间。 
       
         Update_time 
         什么时候数据文件被最后一次更新 
       
         Check_time 
         什么时候表被最后一次检查。不是所有的存储引擎此时都更新，在此情况下，值为NULL。 
       
         Collation 
         表的字符集和整序。 
       
         Checksum 
         活性校验和值。 
       
         Create_options 
         和CREATE TABLE同时使用的额外选项。 
       
         Comment 
         创建表时使用的评注（或者有关为什么MySQL可以访问表信息的说明）。 
       
     

Name	表的名称
Engine	表的存储引擎。在MySQL 4.1.2之前，本值被标记为Type。
Version	表的.frm文件的版本号
Row_format	行存储格式（Fixed, Dynamic, Compressed, Redundant, Compact）。InnoDB表的格式被报告为Redundant或Compact
Rows	行的数目。部分存储引擎，如MyISAM，存储精确的数目。对于其它存储引擎，比如InnoDB，本值是一个大约的数，与实际值相差可达40到50％。在这些情况下，使用SELECT COUNT(*)来获得准确的数目。对于在INFORMATION_SCHEMA数据库中的表，Rows值为NULL。
Avg_row_length	平均的行长度。
Data_length	数据文件的长度。
Max_data_length	数据文件的最大长度。如果给定了数据指针的大小，这是可以被存储在表中的数据的字节总数。
Index_length	索引文件的长度。
Data_free	被整序，但是未使用的字节的数目。
Auto_increment	下一个AUTO_INCREMENT值。
Create_time	表创建时间。
Update_time	什么时候数据文件被最后一次更新
Check_time	什么时候表被最后一次检查。不是所有的存储引擎此时都更新，在此情况下，值为NULL。
Collation	表的字符集和整序。
Checksum	活性校验和值。
Create_options	和CREATE TABLE同时使用的额外选项。
Comment	创建表时使用的评注（或者有关为什么MySQL可以访问表信息的说明）。