text: -- vtab2.test
  -- 
  -- execsql {
  --     BEGIN TRANSACTION;
  --     CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c, UNIQUE(b, c));
  --     CREATE TABLE fkey(
  --       to_tbl,
  --       to_col
  --     );
  --     INSERT INTO "fkey" VALUES('t1',NULL);
  --     COMMIT;
  -- }
  BEGIN TRANSACTION;
  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c, UNIQUE(b, c));
  CREATE TABLE fkey(
  to_tbl,
  to_col
  );
  INSERT INTO "fkey" VALUES('t1',NULL);
  COMMIT;