# Interval literals
<a name="Interval_literals"></a>

Following are rules for working with interval literals that are supported by AWS Clean Rooms Spark SQL.

Use an interval literal to identify specific periods of time, such as `12 hours` or `6 weeks`. You can use these interval literals in conditions and calculations that involve datetime expressions. 

**Note**  
You can't use the INTERVAL data type for columns in AWS Clean Rooms tables.

 An interval is expressed as a combination of the INTERVAL keyword with a numeric quantity and a supported date part, for example `INTERVAL '7 days'` or `INTERVAL '59 minutes'`. You can connect several quantities and units to form a more precise interval, for example: `INTERVAL '7 days, 3 hours, 59 minutes'`. Abbreviations and plurals of each unit are also supported; for example: `5 s`, `5 second`, and `5 seconds` are equivalent intervals.

If you don't specify a date part, the interval value represents seconds. You can specify the quantity value as a fraction (for example: `0.5 days`).

## Examples
<a name="section_interval-literals-examples"></a>

The following examples show a series of calculations with different interval values.

The following example adds 1 second to the specified date.

```
select caldate + interval '1 second' as dateplus from date
where caldate='12-31-2008';
dateplus
---------------------
2008-12-31 00:00:01
(1 row)
```

The following example adds 1 minute to the specified date.

```
select caldate + interval '1 minute' as dateplus from date
where caldate='12-31-2008';
dateplus
---------------------
2008-12-31 00:01:00
(1 row)
```

The following example adds 3 hours and 35 minutes to the specified date.

```
select caldate + interval '3 hours, 35 minutes' as dateplus from date
where caldate='12-31-2008';
dateplus
---------------------
2008-12-31 03:35:00
(1 row)
```

The following example adds 52 weeks to the specified date.

```
select caldate + interval '52 weeks' as dateplus from date
where caldate='12-31-2008';
dateplus
---------------------
2009-12-30 00:00:00
(1 row)
```

The following example adds 1 week, 1 hour, 1 minute, and 1 second to the specified date.

```
select caldate + interval '1w, 1h, 1m, 1s' as dateplus from date
where caldate='12-31-2008';
dateplus
---------------------
2009-01-07 01:01:01
(1 row)
```

The following example adds 12 hours (half a day) to the specified date.

```
select caldate + interval '0.5 days' as dateplus from date
where caldate='12-31-2008';
dateplus
---------------------
2008-12-31 12:00:00
(1 row)
```

The following example subtracts 4 months from March 31, 2023 and the result is November 30, 2022. The calculation considers the number of days in a month.

```
select date '2023-03-31' - interval '4 months';

?column?
---------------------
2022-11-30 00:00:00
```