Add Restarting Sequences When Truncating Tables as a postgres til.

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

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+# 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;
+```