Add Set Seed For Random Number Generator as a postgres til

postgres/set-seed-for-random-number-generator.md

@@ -0,0 +1,42 @@
+# Set Seed For Random Number Generator
+
+In PostgreSQL, the internal seed for the random number generator is a
+run-time configuration parameter. This `seed` parameter can be set to a
+particular seed in order to get some determinism from functions that utilize
+the random number generator. The seed needs to be something between `0` and
+`1`.
+
+```sql
+> set seed to 0.1234;
+SET
+
+> select random();
+      random
+-------------------
+ 0.397731185890734
+
+> select random();
+      random
+------------------
+ 0.39575699577108
+(1 row)
+
+> set seed to 0.1234;
+SET
+
+> select random();
+      random
+-------------------
+ 0.397731185890734
+
+> select random();
+      random
+------------------
+ 0.39575699577108
+```
+
+The seed can also be configured with the `setseed()` function.
+
+See [the PostgreSQL
+docs](http://www.postgresql.org/docs/8.3/static/sql-set.html) for more
+details.