How to Determine the Size of a Java.sql.ResultSet?

Calculating the Size of a java.sql.ResultSet

While working with SQL databases, determining the size or number of rows in a result set is a common requirement. However, unlike most data structures, java.sql.ResultSet does not offer a direct method to obtain its size.

Solution 1: SELECT COUNT(*) Query

A straightforward approach is to execute a SELECT COUNT(*) query against the table or view from which the result set was obtained. This query returns the total number of rows in the result set.

Statement statement = connection.createStatement();
ResultSet countResult = statement.executeQuery("SELECT COUNT(*) FROM <table_name>");

int size = countResult.getInt(1);  // Assuming the result contains a single column</table_name>

Solution 2: ResultSet Navigation

Alternatively, you can utilize the following code to determine the size of the result set:

int size = 0;
if (rs != null) {
    rs.last();  // Move the cursor to the last row
    size = rs.getRow();  // Retrieve the row ID, which represents the size of the result set
}

Advantages of the Second Solution

While the SELECT COUNT(*) query is a standard approach, it has the following drawbacks:

• It requires an additional query execution, which can be time-consuming for large result sets.
• It doesn't account for any filtering or sorting applied to the result set.

In contrast, the second solution only navigates through the existing result set, making it more efficient for large result sets. Additionally, it considers any filters or sorts applied before retrieving the row count.

The above is the detailed content of How to Determine the Size of a Java.sql.ResultSet?. For more information, please follow other related articles on the PHP Chinese website!