DATEADD is a function in MS's TransactSQL for Sql Server. I do not know that DBIsam supports it, and it is not listed in DBIsam's list of supported functions here:
Generally, date functions are not portable across different SQL engines, and from that list, one possibility might be to use the
EXTRACT function instead:
The EXTRACT function returns a specific value from a date, time, or timestamp value. The syntax is as follows:
FROM column_reference or expression)
column_reference or expression)
Use EXTRACT to return the year, month, week, day of week, day, hours, minutes, seconds, or milliseconds from a date, time, or timestamp column. EXTRACT returns the value for the specified element as an integer.
The extract_value parameter may contain any one of the specifiers:
Even if you are in a hurry, I strngly recommend that you study that page carefully.
UPDATE: From googling
dbisam dateadd it looks like Elevate don't have a good answer for an equivalent to
DATEADD. One of the hits is this thread:
which suggested an alternative way to do it using Delphi's built-in date functions (like
IncMonth which I suggested you use in an answer to another q. Basically, you would calculate the start- and end-dates of a range of dates, then convert them to strings to construct a WHERE clause with a column date (from your db) which is equal to or greater than the start date and less or equal to the end date.