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25.39.8 The INFORMATION_SCHEMA INNODB_COLUMNS Table

Contents

The INNODB_COLUMNS table provides metadata about InnoDB table columns.

For related usage information and examples, see Section 15.14.3, “InnoDB INFORMATION_SCHEMA Schema Object Tables”.

The INNODB_COLUMNS table has these columns:

  • TABLE_ID

    An identifier representing the table associated with the column; the same value as INNODB_TABLES.TABLE_ID.

  • NAME

    The name of the column. These names can be uppercase or lowercase depending on the lower_case_table_names setting. There are no special system-reserved names for columns.

  • POS

    The ordinal position of the column within the table, starting from 0 and incrementing sequentially. When a column is dropped, the remaining columns are reordered so that the sequence has no gaps. The POS value for a virtual generated column encodes the column sequence number and ordinal position of the column. For more information, see the POS column description in Section 25.39.30, “The INFORMATION_SCHEMA INNODB_VIRTUAL Table”.

  • MTYPE

    Stands for “main type”. A numeric identifier for the column type. 1 = VARCHAR, 2 = CHAR, 3 = FIXBINARY, 4 = BINARY, 5 = BLOB, 6 = INT, 7 = SYS_CHILD, 8 = SYS, 9 = FLOAT, 10 = DOUBLE, 11 = DECIMAL, 12 = VARMYSQL, 13 = MYSQL, 14 = GEOMETRY.

  • PRTYPE

    The InnoDB “precise type”, a binary value with bits representing MySQL data type, character set code, and nullability.

  • LEN

    The column length, for example 4 for INT and 8 for BIGINT. For character columns in multibyte character sets, this length value is the maximum length in bytes needed to represent a definition such as VARCHAR(N); that is, it might be 2*N, 3*N, and so on depending on the character encoding.

  • HAS_DEFAULT

    A boolean value indicating whether a column that was added instantly using ALTER TABLE ... ADD COLUMN with ALGORITHM=INSTANT has a default value. All columns added instantly have a default value, which makes this column an indicator of whether the column was added instantly.

  • DEFAULT_VALUE

    The initial default value of a column that was added instantly using ALTER TABLE ... ADD COLUMN with ALGORITHM=INSTANT. If the default value is NULL or was not specified, this column reports NULL. An explicitly specified non-NULL default value is shown in an internal binary format. Subsequent modifications of the column default value do not change the value reported by this column.

Example

  1. mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_COLUMNS where TABLE_ID = 71\G
  2. *************************** 1. row ***************************
  3.      TABLE_ID: 71
  4.          NAME: col1
  5.           POS: 0
  6.         MTYPE: 6
  7.        PRTYPE: 1027
  8.           LEN: 4
  9.   HAS_DEFAULT: 0
  10. DEFAULT_VALUE: NULL
  11. *************************** 2. row ***************************
  12.      TABLE_ID: 71
  13.          NAME: col2
  14.           POS: 1
  15.         MTYPE: 2
  16.        PRTYPE: 524542
  17.           LEN: 10
  18.   HAS_DEFAULT: 0
  19. DEFAULT_VALUE: NULL
  20. *************************** 3. row ***************************
  21.      TABLE_ID: 71
  22.          NAME: col3
  23.           POS: 2
  24.         MTYPE: 1
  25.        PRTYPE: 524303
  26.           LEN: 10
  27.   HAS_DEFAULT: 0
  28. DEFAULT_VALUE: NULL

Contents Haut

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.


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