Why Does My Java PreparedStatement Throw a Syntax Error, and How Can I Fix It?

PreparedStatement Syntax Error

When using Java PreparedStatements, it's crucial to ensure correct syntax to avoid errors. The provided code snippet encounters a syntax error due to a mistaken method call.

The select1 method receives a prepared statement sql and an integer randNum and attempts to execute it. However, the error message indicates a syntax issue with the SQL statement:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?)' at line 1

The issue lies in the return statement within the select1 method:

return this.stmt.executeQuery(sql);

This line incorrectly attempts to execute the SQL statement as a normal statement instead of a prepared statement. The correct method to execute a prepared statement is executeQuery().

To resolve the error, replace the code with the correct executeQuery() call:

return this.stmt.executeQuery();

Updated Code:

public ResultSet select1(String sql, int randNum) {
    try {
        this.stmt = con.prepareStatement(sql);
        stmt.setInt(1, randNum);
        return this.stmt.executeQuery(); // Call PreparedStatement.executeQuery
    } catch (SQLException e) {
        e.printStackTrace();
        return null;
    }
}

Note:

The syntax for the SQL query must also be correct. In this case, the missing backticks around value in the WHERE clause were causing the error. The correct SQL statement should be:

String selectSql1 = "SELECT `value` FROM `sampling_numbers` WHERE `value` < ?";

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