Add Determine Types Of JSONB Records as a postgres til

postgres/determine-types-of-jsonb-records.md

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+# Determine Types Of JSONB Records
+
+You can stick several different things into a [JSONB postgres
+column](https://www.postgresql.org/docs/9.4/datatype-json.html).
+
+> Possible types are object, array, string, number, boolean, and null.
+
+If you are trying to audit what is in them, you might reach for:
+
+```sql
+> select pg_typeof(my_jsonb_column) from my_table;
+```
+
+That is just gonna spit out `jsonb` over and over, like, I already know that.
+
+What you really want to know is, is the top-level thing an _object_, an
+_array_, or maybe just a _string_ or _number_. There are specific JSON
+processing functions for this, `json_typeof` and `jsonb_typeof` which you can
+call like so:
+
+```sql
+> select jsonb_typeof(my_jsonb_column) from my_table;
+ jsonb_typeof
+--------------
+ object
+ array
+ ...
+```
+
+[source](https://www.postgresql.org/docs/9.5/functions-json.html)