Interval '1 hour' / double precision '1.5' Also, the + and * operators come in commutative pairs (for example both date + integer and integer + date) we show only one of each such pair.ĭouble precision '3.5' * interval '1 hour' For brevity, these variants are not shown separately. Similarly, a date value is assumed to represent midnight in the TimeZone zone when comparing it to a timestamp.Īll the functions and operators described below that take time or timestamp inputs actually come in two variants: one that takes time with time zone or timestamp with time zone, and one that takes time without time zone or timestamp without time zone. ![]() When comparing a timestamp without time zone to a timestamp with time zone, the former value is assumed to be given in the time zone specified by the TimeZone configuration parameter, and is rotated to UTC for comparison to the latter value (which is already in UTC internally). ![]() Dates and timestamps (with or without time zone) are all comparable, while times (with or without time zone) and intervals can only be compared to other values of the same data type. In addition, the usual comparison operators shown in Table 9.1 are available for the date/time types. You should be familiar with the background information on date/time data types from Section 8.5. For formatting functions, refer to Section 9.8. Table 9.30 illustrates the behaviors of the basic arithmetic operators ( +, *, etc.). Table 9.31 shows the available functions for date/time value processing, with details appearing in the following subsections. A column default can use volatile functions, for example random() or functions referring to the current time this is not allowed for generated columns.9.9.1. A column default may not refer to other columns of the table a generation expression would normally do so. The column default is evaluated once when the row is first inserted if no other value was provided a generated column is updated whenever the row changes and cannot be overridden. In INSERT or UPDATE commands, a value cannot be specified for a generated column, but the keyword DEFAULT may be specified.Ĭonsider the differences between a column with a default and a generated column. See CREATE TABLE for more details.Ī generated column cannot be written to directly. ![]() The keyword STORED must be specified to choose the stored kind of generated column. Height_in numeric GENERATED ALWAYS AS (height_cm / 2.54) STORED ![]() To create a generated column, use the GENERATED ALWAYS AS clause in CREATE TABLE, for example: PostgreSQL currently implements only stored generated columns. Thus, a virtual generated column is similar to a view and a stored generated column is similar to a materialized view (except that it is always updated automatically). A virtual generated column occupies no storage and is computed when it is read. A stored generated column is computed when it is written (inserted or updated) and occupies storage as if it were a normal column. There are two kinds of generated columns: stored and virtual. Thus, it is for columns what a view is for tables. A generated column is a special column that is always computed from other columns.
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