Add String Contains Another String as a postgres til.

README.md

@@ -56,6 +56,7 @@ 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)
+- [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)
 - [Turning Timing On](postgres/turning-timing-on.md)

postgres/string-contains-another-string.md

@@ -0,0 +1,26 @@
+# String Contains Another String
+
+You can check if a string *contains* another string using the `position`
+function.
+
+```sql
+> select position('One' in 'One Two Three');
+ position
+----------
+        1
+```
+
+It returns the 1-based index of the first character of the first match of
+that substring.
+
+```sql
+> select position('Four' in 'One Two Three');
+ position
+----------
+        0
+```
+
+If the substring doesn't appear within the string, then the result is 0.
+
+Thus, you can determine if a string *contains* another string by checking if
+the value resulting from `position` is greater than 0.