This statement

CREATE TABLE t1 (

  c1 INT PRIMARY KEY

) ENGINE MEMORY

makes c1 the primary key and uses the default index type (HASH for MEMORY engine).

If we want to use a BTREE index instead, then this does not work:

CREATE TABLE t1 (

  c1 INT PRIMARY KEY TYPE BTREE

) ENGINE MEMORY

the SQL parser bails out at 'TYPE BTREE'

If written like so, it works again:

CREATE TABLE t1 (

  c1 INT,

  PRIMARY KEY (c1) TYPE BTREE

) ENGINE MEMORY

The request is to extend the parser to accept an index TYPE when a column definition contains an attribute that would add an index for that column. That is not just PRIMARY KEY, but also UNIQUE.