What diagnostic methods can be applied when working with a database?

Methods for diagnosing issues and errors when working with a database include:

• Logging queries and errors: Analyzing logs helps identify problematic queries and connection errors.
• Query profiling: Using EXPLAIN or similar tools to assess query efficiency.
• Monitoring database status: Checking CPU load, memory, disk, locks, and transaction contention.
• Connection testing: Verifying database accessibility and connection parameters.
• Using tracing tools: For example, JDBC drivers can support SQL query tracing.
• Data integrity checks: Running tests and checks to identify corruption or inconsistencies.

Example in Java for logging errors during a query execution:

try (Connection conn = dataSource.getConnection();
     PreparedStatement stmt = conn.prepareStatement("SELECT * FROM users WHERE id = ?")) {
    stmt.setInt(1, userId);
    ResultSet rs = stmt.executeQuery();
    // process results
} catch (SQLException e) {
    logger.error("Error executing database query", e);
}