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Add Get Idea Of What Is In A JSON Column as a MySQL TIL

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README.md
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@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
_1696 TILs and counting..._
_1697 TILs and counting..._
See some of the other learning resources I work on:
@@ -763,6 +763,7 @@ If you've learned something here, support my efforts writing daily TILs by
- [Doing Date Math](mysql/doing-date-math.md)
- [Dump A Database To A File](mysql/dump-a-database-to-a-file.md)
- [Echo A Message From A SQL File](mysql/echo-a-message-from-a-sql-file.md)
- [Get Idea Of What Is In A JSON Column](mysql/get-idea-of-what-is-in-a-json-column.md)
- [Ignore Duplicates When Inserting Records](mysql/ignore-duplicates-when-inserting-records.md)
- [List Databases And Tables](mysql/list-databases-and-tables.md)
- [Run Statements In A Transaction](mysql/run-statements-in-a-transaction.md)

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mysql/get-idea-of-what-is-in-a-json-column.md Normal file
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# Get Idea Of What Is In A JSON Column
While digging through some data trying to reacquaint myself with the overall
schema and data model, I ran into an issue selecting rows from this
`content_resource` table. There was so much text packed in to the `"body"`,
`"summary"`, and `"description"` key-value pairs of `fields` JSON column that a
simple `select * ... limit 3;` was overwhelming the screen with text and table
formatting characters (i.e. `+------+-------`).
I figured the `fields` JSON followed a reliable structure, at least for records
of the same `type`. So, let's start by only grabbing the
[`json_keys`](https://dev.mysql.com/doc/refman/8.4/en/json-search-functions.html#function_json-keys)
so that I can get a sense of the shape of the JSON.
```sql
select id, json_keys(fields)
from content_resource
where type = 'post'
limit 3;
+-----+-----------------------------------------------------------------------------------------------------------+
| id | json_keys(`fields`) |
+-----+-----------------------------------------------------------------------------------------------------------+
| 1 | ["body", "slug", "state", "title", "summary", "postType", "visibility", "description", "originalLessonId"] |
| 2 | ["body", "slug", "state", "title", "summary", "postType", "visibility", "description", "originalLessonId"] |
| 3 | ["body", "slug", "state", "title", "summary", "postType", "visibility", "description", "originalLessonId"] |
+-----+-----------------------------------------------------------------------------------------------------------+
```
For the `post` type, I see the same keys for this sampling of rows. Now I have
an idea what keys are present and can start digging in further.
My next query might look something like this:
```sql
select id, fields->'$.slug', fields->'$.title', fields->'$.state'
from content_resource
where type = 'post'
limit 3;
```