How to check if primary key exists in MySQL

Question

I have tried several sql scripts but failed on it. Here is the one where I got close to:

SELECT *
FROM INFORMATION_SCHEMA.STATISTICS
WHERE table_schema = schema()
AND   table_name   = 'my_table_name'
AND   index_name   = 'column_name';

Answer 1

I think you need below statement

https://www.db-fiddle.com/f/jbdzXwpWkYichsBL1ib2Rj/2

select constraint_name
  from information_schema.table_constraints
 where table_name = 'mytable'
   and table_schema = 'myschema'
   and constraint_name = 'PRIMARY';

or below https://www.db-fiddle.com/f/jbdzXwpWkYichsBL1ib2Rj/3

SELECT EXISTS(
  SELECT 1
  FROM information_schema.columns
  WHERE 
     table_name='messages'
     and column_key = 'PRI'
) As HasPrimaryKey;