Add Show Indexes For A Table as a mysql til

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_535 TILs and counting..._
+_536 TILs and counting..._
 
 ---
 
@@ -232,6 +232,7 @@ _535 TILs and counting..._
 ### MySQL
 
 - [List Databases And Tables](mysql/list-databases-and-tables.md)
+- [Show Indexes For A Table](mysql/show-indexes-for-a-table.md)
 
 ### Phoenix
 

mysql/show-indexes-for-a-table.md

@@ -0,0 +1,33 @@
+# Show Indexes For A Table
+
+When describing a table, such as the table `users`:
+
+```sql
+> describe users;
++------------+-----------------------+------+-----+---------+----------------+
+| Field      | Type                  | Null | Key | Default | Extra          |
++------------+-----------------------+------+-----+---------+----------------+
+| id         | mediumint(8) unsigned | NO   | PRI | NULL    | auto_increment |
+| first_name | varchar(80)           | NO   |     | NULL    |                |
+| last_name  | varchar(80)           | NO   |     | NULL    |                |
+| email      | varchar(80)           | NO   | UNI | NULL    |                |
++------------+-----------------------+------+-----+---------+----------------+
+```
+
+I can see in the `Key` column that there is a primary key and a unique key
+for this table on `id` and `email`, respectively.
+
+These keys are indexes. To get more details about each of the indexes on
+this table, we can use the
+[`show indexes`](https://dev.mysql.com/doc/refman/5.7/en/show-index.html)
+command.
+
+```sql
+> show indexes in users;
++-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
+| Table | Non_unique | Key_name     | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
++-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
+| users |          0 | PRIMARY      |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
+| users |          0 | unique_email |            1 | email       | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
++-------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
+```