Add Generate Series Of Numbers as a postgres til.

README.md

@@ -57,6 +57,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Configure The Timezone](postgres/configure-the-timezone.md)
 - [Count Records By Type](postgres/count-records-by-type.md)
 - [Extracting Nested JSON Data](postgres/extracting-nested-json-data.md)
+- [Generate Series Of Numbers](postgres/generate-series-of-numbers.md)
 - [String Contains Another String](postgres/string-contains-another-string.md)
 - [Timestamp Functions](postgres/timestamp-functions.md)
 - [Toggling The Pager In PSQL](postgres/toggling-the-pager-in-psql.md)

postgres/generate-series-of-numbers.md

@@ -0,0 +1,46 @@
+# Generate Series Of Numbers
+
+Postgres has a `generate_series` function that can be used to, well,
+generate a series of something. The simplest way to use it is by giving it
+`start` and `stop` arguments
+
+```sql
+> select generate_series(1,5);
+ generate_series 
+-----------------
+               1
+               2
+               3
+               4
+               5
+```
+
+The default step is 1, so if you want to count backwards, you need to
+specify a negative step
+
+
+```sql
+> select generate_series(5,1,-1);
+ generate_series 
+-----------------
+               5
+               4
+               3
+               2
+               1
+```
+
+You can use a larger step value to, for instance, get only multiples of 3
+
+```sql
+> select generate_series(3,17,3);
+ generate_series 
+-----------------
+               3
+               6
+               9
+              12
+              15
+```
+
+Trying this out with timestamps is left as an exercise for the reader.