From a3927ee02e9c3eaa49b0dffcc1639055a7615b15 Mon Sep 17 00:00:00 2001
From: jbranchaud <jbranchaud@gmail.com>
Date: Fri, 4 Aug 2023 12:57:03 -0500
Subject: [PATCH] Add Different Ways To Define An Interval as a PostgreSQL TIL

---
 README.md                                     |  3 +-
 .../different-ways-to-define-an-interval.md   | 51 +++++++++++++++++++
 2 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 postgres/different-ways-to-define-an-interval.md

diff --git a/README.md b/README.md
index d644ee5..6d1c0f8 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1327 TILs and counting..._
+_1328 TILs and counting..._
 
 ---
 
@@ -644,6 +644,7 @@ _1327 TILs and counting..._
 - [Determine Types Of JSONB Records](postgres/determine-types-of-jsonb-records.md)
 - [Determining The Age Of Things](postgres/determining-the-age-of-things.md)
 - [Difference Between Explain And Explain Analyze](postgres/difference-between-explain-and-explain-analyze.md)
+- [Different Ways To Define An Interval](postgres/different-ways-to-define-an-interval.md)
 - [Dump All Databases To A SQL File](postgres/dump-all-databases-to-a-sql-file.md)
 - [Dump And Restore A Database](postgres/dump-and-restore-a-database.md)
 - [Dump The SQL Needed To Recreate A Table](postgres/dump-the-sql-needed-recreate-a-table.md)
diff --git a/postgres/different-ways-to-define-an-interval.md b/postgres/different-ways-to-define-an-interval.md
new file mode 100644
index 0000000..3c614fc
--- /dev/null
+++ b/postgres/different-ways-to-define-an-interval.md
@@ -0,0 +1,51 @@
+# Different Ways To Define An Interval
+
+There are several different ways in PostgreSQL to define an `interval` data
+type. An `interval` is useful because it can represent a discrete chunk of
+time. This is handy for doing date math.
+
+Here are four different ways to define an `interval`:
+
+1. Use the `interval` keyword with a string
+
+```sql
+> select interval '3 days';
+ interval
+----------
+ 3 days
+(1 row)
+```
+
+2. Cast a string to the `interval` type
+
+```sql
+> select '3 days'::interval;
+ interval
+----------
+ 3 days
+(1 row)
+```
+
+3. The `@` operator is a finicky syntax for declaring an interval
+
+```sql
+> select @ 3 days;
+ days
+------
+    3
+(1 row)
+```
+
+4. The [`make_interval`
+   function](https://www.postgresql.org/docs/current/functions-datetime.html)
+   can take various forms of arguments to construct an interval
+
+```sql
+> select make_interval(days => 3);
+ make_interval
+---------------
+ 3 days
+(1 row)
+```
+
+[source](https://www.postgresql.org/docs/current/datatype-datetime.html#DATATYPE-INTERVAL-INPUT)