1. A computer implemented method, comprising: in response to a query statement for accessing a relational database, generating a syntax tree representing semantic information of the query statement, the query statement having a wildcard parameter and implemented as an object of a SQL; and predicting a data type of the wildcard parameter based on the semantic information obtained from the syntax tree in view of a structure representing the syntax tree, wherein the predicted data type of the wildcard parameter is used to access the corresponding entry of the relational database.