If you need a fully consistent database with SQL semantics, Cassandra is NOT the solution for you. Cassandra supports key-value lookups. It does not support SQL queries. Data in Cassandra is "eventually consistent". Concurrent lookups of data may be inconsistent, but eventually lookups are consistent.
If you need strict semantics and need support for SQL queries, choose another solution such as MySQL, PostGres, or combine use of Cassandra with Solr.
