Cannot parse sqlite `NVARCHAR` correctly

SQLite uses NVARCHAR() for VARCHAR() but it appears sqlglot does not support this.

sqlglot.errors.ParseError: Expecting ). Line 1, Col: 19.
  CREATE TABLE z (a NVARCHAR(200) NOT NULL)

I think the correct thing is to map NVARCHAR to VARCHAR in the sqlite dialect definition’s keywords block, and that works the case above, but this case still fails:

sqlglot.errors.ParseError: Expecting ). Line 5, Col: 12.

CREATE TABLE "Track"
(
    "TrackId" INTEGER  NOT NULL,
    "Name" NVARCHAR(200)  NOT NULL,
    "AlbumId" INTEGER,
    "MediaTypeId" INTEGER  NOT NULL,
    "GenreId" INTEGER,

Not sure why the latter case isn’t fixed by adding the NVARCHAR mapping to the VARCHAR token type.

[tobymao]

i’ve added constraint and foreign key parsing

[tobymao]

https://github.com/tobymao/sqlglot/commit/9059c552589b2d737d8e87b45728377adf1e0407