Add Determine Types Of JSONB Records as a postgres til

README.md

@@ -9,7 +9,7 @@ and pairing with smart people at Hashrocket.
 
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-_932 TILs and counting..._
+_933 TILs and counting..._
 
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@@ -457,6 +457,7 @@ _932 TILs and counting..._
 - [Day Of Week For A Date](postgres/day-of-week-for-a-date.md)
 - [Default Schema](postgres/default-schema.md)
 - [Defining Arrays](postgres/defining-arrays.md)
+- [Determine Types Of JSONB Records](postgres/determine-types-of-jsonb-records.md)
 - [Determining The Age Of Things](postgres/determining-the-age-of-things.md)
 - [Difference Between Explain And Explain Analyze](postgres/difference-between-explain-and-explain-analyze.md)
 - [Dump And Restore A Database](postgres/dump-and-restore-a-database.md)

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)