ResultSetMetaData

ResultSetMetaData is an interface in the Java Platform, Standard Edition, part of the java.sql package. It describes the metadata of the columns in a ResultSet, providing information about the structure and properties of the returned data. JDBC drivers implement this interface to expose database-specific details to applications, enabling dynamic processing of query results without hard-coded column assumptions.

A ResultSetMetaData object is obtained from a ResultSet by calling getMetaData. This metadata is useful for applications that need to adapt to varying query results, such as data mappers, reporting tools, or generic data access layers. It allows code to discover the number of columns, as well as descriptive information for each column, at runtime.

Common capabilities exposed by ResultSetMetaData include: the number of columns; column names and labels; catalog, schema, and table names; SQL type and database-type name; column display size; precision and scale for numeric columns; and flags describing nullability and other column properties (such as whether a column is auto-increment or writable). The exact set of available details and their values can vary by JDBC driver and database, and column indices are usually one-based.

In practice, applications use this metadata to map ResultSet contents to generic data structures, implement dynamic report generation, or provide user interfaces that reflect the structure of a query results without prior knowledge of the schema.