Datatypes

DataJoint supports the following datatypes. To conserve database resources, use the smallest and most restrictive datatype sufficient for your data. This also ensures that only valid data are entered into the pipeline.

Most common datatypes

  • tinyint: an 8-bit integer number, ranging from -128 to 127.
  • tinyint unsigned: an 8-bit positive integer number, ranging from 0 to 255.
  • smallint: a 16-bit integer number, ranging from -32,768 to 32,767.
  • smallint unsigned: a 16-bit positive integer, ranging from 0 to 65,535.
  • int: a 32-bit integer number, ranging from -2,147,483,648 to 2,147,483,647.
  • int unsigned: a 32-bit positive integer, ranging from 0 to 4,294,967,295.
  • enum: one of several explicitly enumerated values specified as strings. Use this datatype instead of text strings to avoid spelling variations and to save storage space. For example, the datatype for an anesthesia attribute could be enum("urethane", "isoflurane", "fentanyl"). Do not use enums in primary keys due to the difficulty of changing their definitions consistently in multiple tables.
  • date: date as 'YYYY-MM-DD'.
  • time: time as 'HH:MM:SS'.
  • datetime: Date and time to the second as 'YYYY-MM-DD HH:MM:SS'
  • timestamp: Date and time to the second as 'YYYY-MM-DD HH:MM:SS'. The default value may be set to CURRENT_TIMESTAMP. Unlike datetime, a timestamp value will be adjusted to the local time zone.
  • char(N): a character string up to N characters (but always takes the entire N bytes to store).
  • varchar(N): a text string of arbitrary length up to N characters that takes M+1 or M+2 bytes of storage, where M is the actual length of each stored string.
  • float: a single-precision floating-point number. Takes 4 bytes. Single precision is sufficient for many measurements.
  • double: a double-precision floating-point number. Takes 8 bytes. Because equality comparisons are error-prone, neither float nor double should be used in primary keys.
  • decimal(N,F): a fixed-point number with N total decimal digits and F fractional digits. This datatype is well suited to represent numbers whose magnitude is well defined and does not warrant the use of floating-point representation or requires precise decimal representations (e.g. dollars and cents). Because of its well-defined precision, decimal values can be used in equality comparison and be included in primary keys.
  • longblob: arbitrary numeric array (e.g. matrix, image, structure), up to 4 GiB in size. Numeric arrays are compatible between MATLAB and Python (NumPy). The longblob datatype can be configured to store data externally.

Less common (but supported) datatypes

  • decimal(N,F) unsigned: same as decimal, but limited to nonnegative values.
  • mediumint a 24-bit integer number, ranging from -8,388,608 to 8,388,607.
  • mediumint unsigned: a 24-bit positive integer, ranging from 0 to 16,777,216.
  • mediumblob: arbitrary numeric array, up to 16 MiB
  • blob: arbitrary numeric array, up to 64 KiB
  • tinyblob: arbitrary numeric array, up to 256 bytes (actually smaller due to header info).

Datatypes not (yet) supported

  • binary
  • text
  • longtext
  • bit

For additional information about these datatypes, see http://dev.mysql.com/doc/refman/5.6/en/data-types.html