Fix json example

Because of sqlite's flexible typing, even though the column was declared as jsonb, the values are stored as the TEXT-typed json because they're converted to strings by Value/Scan. If the table is strict with a BLOB column, the example fails because of the type mismatch. This can be fixed by using the `jsonb()` function to convert incoming string-typed json and the `json()` function to convert outgoing binary-typed jsonb. The example is expanded to show both of these approaches.

Note that both approaches use the same string-typed marshalling functions because the conversion to jsonb occurs within sqlite3, not within the Go code. SQLite docs state that the binary format is internal and applications shouldn't try to generate it: https://sqlite.org/json1.html#jsonb

_example/json/json.go

@@ -33,7 +33,9 @@ func main() {
 	}
 	defer db.Close()
 
-	_, err = db.Exec(`create table foo (tag jsonb)`)
+	// Using a json-typed column
+	// Verify type: `create table foo (tag text) strict`
+	_, err = db.Exec(`create table foo (tag json)`)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -78,4 +80,50 @@ func main() {
 		log.Fatal(err)
 	}
 	fmt.Println(country)
+
+	// Using a jsonb-typed column
+	// Verify type: `create table bar (tag blob) strict`
+	_, err = db.Exec(`create table bar (tag jsonb)`)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	stmt, err = db.Prepare("insert into bar(tag) values(jsonb(?))")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer stmt.Close()
+	_, err = stmt.Exec(`{"name": "mattn", "country": "japan"}`)
+	if err != nil {
+		log.Fatal(err)
+	}
+	_, err = stmt.Exec(`{"name": "michael", "country": "usa"}`)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = db.QueryRow("select tag->>'country' from bar where tag->>'name' = 'mattn'").Scan(&country)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(country)
+
+	err = db.QueryRow("select json(tag) from bar where tag->>'name' = 'mattn'").Scan(&tag)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(tag.Name)
+
+	tag.Country = "日本"
+	_, err = db.Exec(`update bar set tag = jsonb(?) where tag->>'name' == 'mattn'`, &tag)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = db.QueryRow("select tag->>'country' from bar where tag->>'name' = 'mattn'").Scan(&country)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(country)
 }