Methods and systems for query optimization for a multi-tenant database system are provided. Some embodiments comprise receiving at a network interface of a server in a multi-tenant database system an original query transmitted to the multi-tenant database system by a user associated with a tenant, wherein the original query is associated with data accessible by the tenant, and wherein the multi-tenant database system includes at least a first index and a second index. Metadata associated with the data is retrieved, wherein at least a portion of the data is stored in a common table within the multi-tenant database system. A tenant-selective query syntax is determined by analyzing at least one of metadata generated from information about the tenant or metadata generated from the data accessible by the tenant. An improved query is then generated using the query syntax, wherein the improved query is based at least in part upon the original query and a result of a join between a first number of rows associated with the first index and a second number of rows associated with the second index.