17. One or more computer-readable media storing executable instructions that, when executed by one or more processors, cause the one or more processors to perform acts comprising: receiving a query request for data stored in at least two databases, the query request based at least in part on a business model, the business model comprising one or more business elements; generating a uniform query that masks a difference among the at least two different databases by converting the query request into an execution mode that matches with the at least two different databases to be queried based at least in part on a conversion rule between the business model and a storage model, the storage model comprising attribute information of the at least two databases to be queried and the conversion rule comprising a corresponding relationship between the one or more business elements and one or more attributes in the at least two databases to be queried; and accessing the at least two databases according to the execution mode; and upon determining that an amount of concurrent accesses to one of the at least two different databases according to the one or more execution modes exceeds a predetermined amount, delaying a subsequent access to the one of the at least two different databases, or accessing a backup database, if available, of the one of the at least two different databases, the backup database having less concurrent accesses than the one of the at least two different databases.
17. One or more computer-readable media storing executable instructions that, when executed by one or more processors, cause the one or more processors to perform acts comprising: receiving a query request for data stored in at least two databases, the query request based at least in part on a business model, the business model comprising one or more business elements; generating a uniform query that masks a difference among the at least two different databases by converting the query request into an execution mode that matches with the at least two different databases to be queried based at least in part on a conversion rule between the business model and a storage model, the storage model comprising attribute information of the at least two databases to be queried and the conversion rule comprising a corresponding relationship between the one or more business elements and one or more attributes in the at least two databases to be queried; and accessing the at least two databases according to the execution mode; and upon determining that an amount of concurrent accesses to one of the at least two different databases according to the one or more execution modes exceeds a predetermined amount, delaying a subsequent access to the one of the at least two different databases, or accessing a backup database, if available, of the one of the at least two different databases, the backup database having less concurrent accesses than the one of the at least two different databases. 20. The one or more computer-readable media of claim 17 , wherein converting the query request comprises one of: converting the query request into an execution mode that matches with respective storage engine types of the at least two different databases; or converting the query request into the execution mode by using a storage acquisition condition as a query condition, and screening an access result acquired from each database of the at least two databases based at least in part on a result filtering condition, wherein the query request comprises a storage acquisition condition and a result filtering condition based at least in part on the business elements.