SQL can include invalid type names and duplicate columns

E.g. will happily generate something like this:

```sql
CREATE TABLE IF NOT EXISTS "users" (
  "signed_in" timestamp | null NOT NULL
);
```

Where the `|` is an invalid character.

Or duplicated columns like:


```sql
CREATE TABLE IF NOT EXISTS "users" (
  "id" serial NOT NULL PRIMARY KEY,
  "id" uuid NOT NULL
)
```