Function json_exists 

pub fn json_exists<'a, L>(left: L, path: &'a str) -> SQL<'a, SQLiteValue<'a>>
where
    L: ToSQL<'a, SQLiteValue<'a>>,

Builds json_type(left, path) IS NOT NULL: the JSON document has a value at path (a JSON null counts as present).

Examples

let column = SQL::<SQLiteValue>::raw("metadata");
let condition = json_exists(column, "$.theme");
assert_eq!(condition.sql(), "json_type( metadata , ? ) IS NOT NULL");