If you specify an AT clause for a TIME[(n)] without time zone target data type, an error is returned.
If you specify an AT clause for a TIME[(n)] WITH TIME ZONE target data type, the following table shows the result of the CAST function or Teradata conversion based on the options specified. If the target precision is higher than the source precision, trailing zeros are added in the result to adjust the precision. If the target precision is lower than the source precision, an error is returned.
| Option | time_expression Data Type | Action |
|---|---|---|
| AT LOCAL | With or without TIME ZONE | |
| AT SOURCE (where SOURCE is keyword and not column reference) |
WITH TIME ZONE | Result is formed from source time_expression (in UTC) and time zone displacement based on current session time zone. Data type of time_expression without time zone is same as not specifying AT clause. |
| Without TIME ZONE | Result is formed from time portion of source time_expression (in UTC) and time zone displacement associated with time_expression. Same as not specifying AT clause. |
|
| AT SOURCE TIME ZONE | WITH TIME ZONE | Result is formed from time portion of source time_expression (in UTC) and time zone displacement associated with time_expression. Same as not specifying AT clause. |
| Without TIME ZONE | Returns error. | |
| AT [ TIME ZONE ] expression | With or without TIME ZONE | Result is formed from time portion of source time_expression (in UTC) and time zone displacement defined by expression. |
| With or without TIME ZONE | Result is formed from time portion of source time_expression (in UTC) and time zone displacement based on time_zone_string. Time zone displacement is based on time_zone_string, CURRENT_TIMESTAMP AT '00:00', and TIME value of time_zone_string at UTC. |