How do you get whether a column is a primary key in MySQL?

To get whether a column is a primary key, use COLUMN_NAME and COLUMN_KEY='PRI'. With that, the entire syntax is as follows −

select column_name, case when column_key= 'PRI' then 'yourMessage1' else ''yourMessage2' end as anyAliasName
from information_schema.columns
where table_schema =database()
and `table_name` = yourTableName
order by `table_name`, ordinal_position;

To understand the above syntax, let us create a table −

mysql> create table DemoTable1886
   (
   Id int NOT NULL,
   FirstName varchar(20),
   LastName varchar(20),
   Age int,
   DateOfBirth datetime,
   Education varchar(40),
   PRIMARY KEY(Id)
   );
Query OK, 0 rows affected (0.00 sec)

Here is the query to get whether a specific column is a primary key −

mysql> select column_name, case when column_key= 'PRI' then 'This is a Primary key Column' else 'This is not a Primary key Column' end as Output
   from information_schema.columns
   where table_schema =database()
   and `table_name` = 'DemoTable1886'
   order by `table_name`, ordinal_position;

This will produce the following output −

+-------------+--------------------------------+
| COLUMN_NAME | Output                         |
+-------------+--------------------------------+
| Id          | This is a Primary key Column   |
| FirstName   |This is not a Primary key Column|
| LastName    |This is not a Primary key Column|
| Age         |This is not a Primary key Column|
| DateOfBirth |This is not a Primary key Column|
| Education   |This is not a Primary key Column|
+-------------+--------------------------------+
6 rows in set (0.00 sec)