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52 lines
1012 B
Markdown
52 lines
1012 B
Markdown
# Different Ways To Define An Interval
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There are several different ways in PostgreSQL to define an `interval` data
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type. An `interval` is useful because it can represent a discrete chunk of
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time. This is handy for doing date math.
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Here are four different ways to define an `interval`:
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1. Use the `interval` keyword with a string
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```sql
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> select interval '3 days';
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interval
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----------
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3 days
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(1 row)
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```
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2. Cast a string to the `interval` type
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```sql
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> select '3 days'::interval;
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interval
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----------
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3 days
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(1 row)
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```
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3. The `@` operator is a finicky syntax for declaring an interval
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```sql
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> select @ 3 days;
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days
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------
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3
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(1 row)
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```
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4. The [`make_interval`
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function](https://www.postgresql.org/docs/current/functions-datetime.html)
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can take various forms of arguments to construct an interval
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```sql
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> select make_interval(days => 3);
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make_interval
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---------------
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3 days
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(1 row)
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```
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[source](https://www.postgresql.org/docs/current/datatype-datetime.html#DATATYPE-INTERVAL-INPUT)
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