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Conversions Possible for the CAST Function

Table 1. Conversions with CAST
From Data Type To Data Type

Numeric types

Numeric types, [VAR]CHAR, BLOB

[VAR]CHAR

[VAR]CHAR, BLOB, Numeric types, DATE, TIME, TIMESTAMP, BOOLEAN

BLOB

[VAR]CHAR, BLOB, Numeric types, DATE, TIME, TIMESTAMP, BOOLEAN

DATE, TIME

[VAR]CHAR, BLOB, TIMESTAMP

TIMESTAMP

[VAR]CHAR, BLOB, DATE, TIME

BOOLEAN

BOOLEAN, [VAR]CHAR, BLOB

To convert string data types to the BOOLEAN type, the value must be (case-insensitive) 'true' or 'false', or NULL.

Important

Keep in mind that partial information loss is possible.For instance, when you cast the TIMESTAMP data type to the DATE data type, the time-part is lost.

Datetime Formats

To cast string data types to the DATE, TIME or TIMESTAMP data types, you need the string argument to be one of the predefined datetime mnemonics (see [fblangref50-dtyp-tbl-datetimemnemonics]) or a representation of the date in one of the allowed datetime formats (see Datetime Format Syntax),

Table 1. Predefined Datetime Mnemonics

Literal

Description

'NOW'

Current date and time

'TODAY'

Current date

'TOMORROW'

Current date + 1 (day)

'YESTERDAY'

Current date - 1 (day)
Note

Casting the date mnemonics 'TODAY', 'TOMORROW' or 'YESTERDAY' to a TIMESTAMP WITH TIME ZONE will produce a value at 00:00:00 UTC rebased to the session time zone.

For example cast('TODAY' as timestamp with time zone) on 2021-05-02 20:00 - 2021-05-03 19:59 New York (or 2021-05-03 00:00 - 2021-05-03 23:59 UTC) with session time zone America/New_York will produce a value TIMESTAMP '2021-05-02 20:00:00.0000 America/New_York', while cast('TODAY' as date) or CURRENT_DATE will produce either DATE '2021-05-02' or DATE '2021-05-03' depending on the actual date.
Sample Date Literal Interpretations
select
  cast('04.12.2014' as date) as d1, -- DD.MM.YYYY
  cast('04 12 2014' as date) as d2, -- MM DD YYYY
  cast('4-12-2014' as date) as d3,  -- MM-DD-YYYY
  cast('04/12/2014' as date) as d4, -- MM/DD/YYYY
  cast('04.12.14' as date) as d5,   -- DD.MM.YY
  -- DD.MM with current year
  cast('04.12' as date) as d6,
  -- MM/DD with current year
  cast('04/12' as date) as d7,
  cast('2014/12/04' as date) as d8, -- YYYY/MM/DD
  cast('2014 12 04' as date) as d9, -- YYYY MM DD
  cast('2014.12.04' as date) as d10, -- YYYY.MM.DD
  cast('2014-12-04' as date) as d11, -- YYYY-MM-DD
  cast('4 Jan 2014' as date) as d12, -- DD MM YYYY
  cast('2014 Jan 4' as date) as dt13, -- YYYY MM DD
  cast('Jan 4 2014' as date) as dt14, -- MM DD YYYY
  cast('11:37' as time) as t1, -- HH:mm
  cast('11:37:12' as time) as t2, -- HH:mm:ss
  cast('11:31:12.1234' as time) as t3, -- HH:mm:ss.nnnn
  -- DD.MM.YYYY HH:mm
  cast('04.12.2014 11:37' as timestamp) as dt1,
  -- MM/DD/YYYY HH:mm:ss
  cast('04/12/2014 11:37:12' as timestamp) as dt2,
  -- DD.MM.YYYY HH:mm:ss.nnnn
  cast('04.12.2014 11:31:12.1234' as timestamp) as dt3,
  cast('now' as timestamp) as m1,
  cast('today' as date) as m2,
  cast('yesterday' as date) as m3,
  cast('tomorrow' as date) as m4
from rdb$database