Add Restarting Sequences When Truncating Tables as a postgres til.

README.md

@@ -145,6 +145,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [List Database Users](postgres/list-database-users.md)
 - [Max Identifier Length Is 63 Bytes](postgres/max-identifier-length-is-63-bytes.md)
 - [Restart A Sequence](postgres/restart-a-sequence.md)
+- [Restarting Sequences When Truncating Tables](postgres/restarting-sequences-when-truncating-tables.md)
 - [Send A Command To psql](postgres/send-a-command-to-psql.md)
 - [Set Inclusion With hstore](postgres/set-inclusion-with-hstore.md)
 - [Special Math Operators](postgres/special-math-operators.md)

postgres/restarting-sequences-when-truncating-tables.md

@@ -0,0 +1,15 @@
+# Restarting Sequences When Truncating Tables
+
+PostgreSQL's
+[`truncate`](http://www.postgresql.org/docs/current/static/sql-truncate.html)
+feature is a handy way to clear out all the data from a table. If you use
+`truncate` on a table that has a `serial` primary key, you may notice that
+subsequent insertions keep counting up from where you left off. This is
+because the sequence the table is using hasn't been restarted. Sure, you can
+restart it manually or you can tell `truncate` to do it for you. By
+appending `restart identity` to the end of a `truncate` statement, Postgres
+will make sure to restart any associated sequences at `1`.
+
+```
+truncate pokemon, trainers, pokemons_trainers restart identity;
+```