Question
What does the 'java.sql.SQLException: Parameter index out of range (2 > number of parameters, which is 0)' error mean in JDBC?
Answer
The `java.sql.SQLException: Parameter index out of range` error occurs when you attempt to access a parameter in a PreparedStatement that hasn't been set or does not exist. This can happen if you're trying to bind a value to a placeholder in a SQL query that is outside the bounds of the parameters defined in the query.
String sql = "INSERT INTO users (name, email) VALUES (?, ?)";
PreparedStatement pstmt = connection.prepareStatement(sql);
// Correct usage: setting parameters
pstmt.setString(1, "John Doe");
pstmt.setString(2, "[email protected]");
pstmt.executeUpdate();
Causes
- Attempting to set a parameter index that exceeds the number of defined parameters in the SQL query.
- Forgetting to set a parameter before executing the SQL statement.
- Misleading indices due to the incorrect assumption of how parameters are indexed. In PreparedStatement, parameters start at index 1.
Solutions
- Ensure the number of parameters in the SQL query matches the number of values you are trying to set.
- Check the binding of your parameters and the specific indices used in set methods, using correct indices starting from 1.
- In the case of conditional parameters, ensure they are set accordingly before execution.
Common Mistakes
Mistake: Using a parameter index of 0 or a negative index.
Solution: Parameter indices in PreparedStatement must start at 1.
Mistake: Not checking the SQL statement for missing placeholders.
Solution: Ensure that every '?' in your SQL query has a corresponding set method call.
Mistake: Overlooking the number of parameters when modifying queries.
Solution: Always verify that query structures match with the corresponding parameters.
Helpers
- java.sql.SQLException
- Parameter index out of range
- JDBC error handling
- PreparedStatement parameters
- Java SQL exceptions
