PHP MySQL Check If A Table Has A Primary Key

问题

What would I query my MySQL server to check if a table has a primary key or not? Something like:

if(mysql_send("SELECT TABLE table HAS PRIMARY KEY") == TRUE) {
   // do stuff here
}

回答1:

SHOW INDEXES FROM TABLE WHERE Key_name = 'PRIMARY'

回答2:

SELECT EXISTS(
  SELECT 1
  FROM information_schema.columns
  WHERE table_schema = 'db'
     and table_name='table name'
     and column_key = 'PRI'
) As HasPrimaryKey

来源：https://stackoverflow.com/questions/4982558/php-mysql-check-if-a-table-has-a-primary-key