Add Temporary Tables as a postgres til.

postgres/temporary-tables.md

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+# Temporary Tables
+
+Create a temporary table in Postgres like so
+
+```sql
+create temp table posts (
+    ...
+);
+```
+
+This table (and its data) will only last for the duration of the session.
+It is created on a schema specific to temporary tables. It is also worth
+noting that it won't be autovacuumed, so this must be done manually as
+necessary.