The Ultimate Guide to High Availability with MariaDB

Information Schema TABLES Table

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Contents

  1. Examples
    1. View tables in order of size
  2. See also

The Information Schema table shows information about the various non-TEMPORARY tables and views on the server.

It contains the following columns:

ColumnDescription
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
TABLE_TYPEOne of BASE TABLE for a regular table, VIEW for a view, or SYSTEM VIEW for Information Schema tables.
ENGINEStorage Engine.
VERSIONVersion number from the table's .frm file
ROW_FORMATRow format (see InnoDB, Aria and MyISAM row formats).
TABLE_ROWSNumber of rows in the table. Some engines, such as XtraDB and InnoDB may store an estimate.
AVG_ROW_LENGTHAverage row length in the table.
DATA_LENGTHFor InnoDB/XtraDB, the index size, in pages, multiplied by the page size. For Aria and MyISAM, length of the data file, in bytes. For MEMORY, the approximate allocated memory.
MAX_DATA_LENGTHMaximum length of the data file, ie the total number of bytes that could be stored in the table. Not used in XtraDB and InnoDB.
INDEX_LENGTHLength of the index file.
DATA_FREEBytes allocated but unused. For InnoDB tables in a shared tablespace, the free space of the shared tablespace with small safety margin. An estimate in the case of partitioned tables - see the PARTITIONS table.
AUTO_INCREMENTNext AUTO_INCREMENT value.
CREATE_TIMETime the table was created.
UPDATE_TIMETime the table was last updated. On Windows, the timestamp is not updated on update, so MyISAM values will be inaccurate. In InnoDB, if shared tablespaces are used, will be NULL, while buffering can also delay the update, so the value will differ from the actual time of the last UPDATE, INSERT or DELETE.
CHECK_TIMETime the table was last checked. Not kept by all storage engines, in which case will be NULL.
TABLE_COLLATIONCharacter set and collation.
CHECKSUMLive checksum value, if any.
CREATE_OPTIONSExtra CREATE TABLE options.
TABLE_COMMENTTable comment provided when MariaDB created the table.

Although the table is standard in the Information Schema, all but TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE and VERSION are MySQL and MariaDB extensions.

SHOW TABLES lists all tables in a database.

Examples

SELECT * FROM INFORMATION_SCHEMA.TABLES\G
...
*************************** 175. row ***************************
  TABLE_CATALOG: def
   TABLE_SCHEMA: test
     TABLE_NAME: xx4
     TABLE_TYPE: BASE TABLE
         ENGINE: MyISAM
        VERSION: 10
     ROW_FORMAT: Fixed
     TABLE_ROWS: 0
 AVG_ROW_LENGTH: 0
    DATA_LENGTH: 0
MAX_DATA_LENGTH: 1970324836974591
   INDEX_LENGTH: 1024
      DATA_FREE: 0
 AUTO_INCREMENT: NULL
    CREATE_TIME: 2013-10-31 14:45:35
    UPDATE_TIME: 2013-10-31 14:45:35
     CHECK_TIME: NULL
TABLE_COLLATION: latin1_swedish_ci
       CHECKSUM: NULL
 CREATE_OPTIONS: key_block_size=46
  TABLE_COMMENT: 
*************************** 176. row ***************************
  TABLE_CATALOG: def
   TABLE_SCHEMA: test
     TABLE_NAME: xx5
     TABLE_TYPE: BASE TABLE
         ENGINE: InnoDB
        VERSION: 10
     ROW_FORMAT: Compact
     TABLE_ROWS: 0
 AVG_ROW_LENGTH: 0
    DATA_LENGTH: 16384
MAX_DATA_LENGTH: 0
   INDEX_LENGTH: 0
      DATA_FREE: 0
 AUTO_INCREMENT: NULL
    CREATE_TIME: 2013-11-11 09:54:11
    UPDATE_TIME: NULL
     CHECK_TIME: NULL
TABLE_COLLATION: latin1_swedish_ci
       CHECKSUM: NULL
 CREATE_OPTIONS: key_block_size=46
  TABLE_COMMENT: 
...

View tables in order of size

Returns a list of all tables in the database, ordered by size:

SELECT table_schema as `DB`, table_name AS `Table`, 
  ROUND(((data_length + index_length) / 1024 / 1024), 2) `Size (MB)` 
  FROM information_schema.TABLES 
  ORDER BY (data_length + index_length) DESC;

+--------------------+---------------------------------------+-----------+
| DB                 | Table                                 | Size (MB) |
+--------------------+---------------------------------------+-----------+
| wordpress          | wp_simple_history_contexts            |      7.05 |
| wordpress          | wp_posts                              |      6.59 |
| wordpress          | wp_simple_history                     |      3.05 |
| wordpress          | wp_comments                           |      2.73 |
| wordpress          | wp_commentmeta                        |      2.47 |
| wordpress          | wp_simple_login_log                   |      2.03 |
...

See also

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