Explicit data type references are made in SQL statements for the creation of user defined domains and base tables and in the alteration of table definitions.
The permissible data types and their allowable ranges within Mimer SQL are:
In SQL, a temporal value is either a datetime (i.e. a date, a clock time, or a timestamp) or an interval (i.e. a period of time). They consist of a contiguous subset of one or more of the fields: YEAR, MONTH, DAY, HOUR, MINUTE and SECOND. Temporal values follow the usual rules of the Gregorian calendar and the 24-hour clock.
Intervals are either year-month intervals (periods of time involving years and/or months) or day-time intervals (periods of time involving days and/or hours and/or minutes and/or seconds and/or fractions of a second).
Mimer SQL supports the OVERLAPS predicate that compares either a pair of datetimes, or a datetime and an interval, to determine whether the two chronological periods overlap in time.
All numeric data and intervals may be signed. The 45 digit numeric precision also extends to arithmetic, making Mimer SQL ideally suited for applications where high numerical precision and accuracy are required.
A SEQUENCE is a construct that returns integer values regardless of concurrent access to the database system; this eliminates application contention when obtaining a unique numeric key value, a common requirement in transaction processing applications. It is also possible to retrieve the previous value returned to the application. One use for a SEQUENCE is as the default value for a column or domain.
Columns that contain an undefined value are assigned a NULL value. Depending on the context, this is represented in SQL statements either by the keyword NULL or by a host variable associated with an indicator variable.
Mimer SQL supports the CAST function, which explicitly converts between data types.
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