PHP MySQL检查表是否有主键

Question

我会查询MySQL服务器以检查表是否有主键？类似的东西：

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

Answer 1

SHOW INDEXES FROM TABLE WHERE Key_name = 'PRIMARY'

Answer 2

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