DATE and DATETIME data types

Informix®

Informix provides two data types to store date and time information:

DATE = for year, month and day storage.
DATETIME = for year to fraction (1-5) storage.

The DATE type is stored as an INTEGER with the number of days since 1899/12/31.

The DATETIME type can be defined with various time units, by specifying a start and end qualifier. For example, you can define a datetime to store an hour-to-second time value with DATETIME HOUR TO SECOND.

The values of Informix DATETIME can be represented with a character string literal, or as DATETIME() literals:

'2017-12-24 15:45:12.345'  -- a DATETIME YEAR TO FRACTION(3)
'15:45'   -- a DATETIME HOUR TO MINUTE
DATETIME(2017-12-24 12:45) YEAR TO MINUTE
DATETIME(12:45:56.333) HOUR TO FRACTION(3)

Informix is able to convert quoted strings to DATE / DATETIME data, if the string contains matching environment parameters. The string to date conversion rules for DATE is defined by the DBDATE environment variable. The string to datetime format for DATETIME is defined by the GL_DATETIME environment variable.

Note: Within Genero programs, the string representation for DATETIME values is always ISO (YYYY-MM-DD hh:mm:ss.fffff)

Informix supports date arithmetic on DATE and DATETIME values. The result of an arithmetic expression involving dates/times is an INTEGER number of days when only DATE values are used, and an INTERVAL value if a DATETIME is used in the expression.

Informix automatically converts an INTEGER to a DATE when the integer is used to set a value of a date column.

SAP HANA®

SAP HANA provides following data type to store dates:

Table 1. SAP HANA date/time data types
SAP HANA data type	Description
`DATE`	for year, month, day storage
`SECONDDATE`	for year, month, day, hour, minutes, seconds storage
`TIME`	for hour, minutes, seconds storage
`TIMESTAMP`	for year, month, day, hour, minutes, seconds, fraction(7) storage

As Informix, SAP HANA® can convert quoted strings to date-time values. Only one format is possible: 'yyyy-mm-dd' for DATE, 'hh:mm:ss' for TIME, 'yyyy-mm-dd hh:mm:ss' for SECONDDATE and 'yyyy-mm-dd hh:mm:ss:ffffffff' for TIMESTAMP.

In SAP HANA (2.x), does not support date/time computation.

Solution

Use the following conversion rules to map Informix date/time types to SAP HANA date/time types:

Table 2. Informix data types and SAP HANA equivalents
Informix data type	SAP HANA data type
`DATE`	`DATE`
`DATETIME HOUR TO MINUTE`	`TIME`
`DATETIME HOUR TO SECOND`	`TIME`
`DATETIME YEAR TO MINUTE`	`SECONDDATE`
`DATETIME YEAR TO SECOND`	`SECONDDATE`
`DATETIME YEAR TO FRACTION(n)`	`TIMESTAMP`
`DATETIME q1 TO q2` (different from above)	`TIMESTAMP`

The DATE and DATETIME types translation can be controlled with the following FGLPROFILE entries:

dbi.database.dsname.ifxemul.datatype.date = { true | false }
dbi.database.dsname.ifxemul.datatype.datetime = { true | false }

For more details see IBM Informix emulation parameters in FGLPROFILE.

Informix DATETIME that are not with a precision of YEAR TO MINUTE, YEAR TO SECOND or YEAR TO FRACTION() can be stored in SAP HANA TIMESTAMP columns. Missing date or time parts default to 1900-01-01 00:00:00.0. For example, when using a DATETIME MONTH TO MINUTE with the value of "04-23 11:45", the SAP HANA TIMESTAMP value will be "1900-04-23 11:45:00.0".

Date/time SQL functions

Table 3. Informix and SAP HANA date/time SQL functions
Informix	SAP HANA
`today`	`current_date`
`current hour to second`	`current_time`
`current year to fraction(5)`	`current_timestamp`