Question
How can I check if a Java ResultSet is empty?
ResultSet resultSet = statement.executeQuery("SELECT * FROM table_name");
Answer
When working with Java's JDBC API, determining whether a ResultSet contains any data is a common requirement. The ResultSet represents the result set of a database query executed via the Statement object. This guide outlines how to check if a ResultSet is empty before processing its data.
public boolean isResultSetEmpty(ResultSet rs) throws SQLException {
return !rs.first(); // Move the cursor to the first row and check if it exists
}
Causes
- Misunderstanding how ResultSet iterates over rows.
- Assuming ResultSet is empty without checking cursor position.
Solutions
- Use the `first()` method to check if there are any rows.
- Call the `next()` method and reset the cursor if needed.
Common Mistakes
Mistake: Not resetting the cursor after checking with `next()` method.
Solution: Use the `first()` method or store the result from `next()` to avoid cursor issues.
Mistake: Assuming a ResultSet is empty when it is not yet iterated.
Solution: Always check if the ResultSet is moved to the first row before assuming it's empty.
Helpers
- Java ResultSet empty check
- How to check ResultSet is empty
- Java JDBC ResultSet
- Check if ResultSet contains data
- ResultSet cursor position checking
