I read about a lib named WebSqlSync as an answer to this question: Best way to synchronize local HTML5 DB (WebSQL Storage, SQLite) with a server (2 way sync)
When reading the documentation I understood that it was only possible to have a single key field to identify the row to sync. As the example given suggests:
TABLES_TO_SYNC = [
{tableName : 'table1', idName : 'the_id'},
{tableName : 'table2'} //if idName not specified, it will assume that it's "id"
];
I wonders if it would accept several keys to identify the row if a table uses several fields as component of the key, so it would look like this:
{tableName : 'table1', idName : 'id_1,id_2,id_3'},