How to fix 22002: null_value_no_indicator_parameter in PostgreSQL

// This will fail with 22002:
int user_id;
char username[50];
EXEC SQL FETCH user_cursor INTO :user_id, :username;
// If username column contains NULL, error occurs

EXEC SQL FETCH cursor_name INTO :host_variable;

EXEC SQL FETCH cursor_name INTO :host_variable :indicator_variable;

short username_indicator;
char username[50];

EXEC SQL FETCH user_cursor INTO :username :username_indicator;

if (username_indicator == -1) {
    // Value is NULL, handle appropriately
    printf("Username is NULL\n");
    strcpy(username, "unknown");
} else if (username_indicator > 0) {
    // String was truncated
    printf("Warning: username truncated, original length: %d\n", username_indicator);
} else {
    // Use username safely
    printf("Username: %s\n", username);
}

int user_id;
char username[50];
char email[100];
short indicators[3];  // One for each column

EXEC SQL FETCH cursor INTO :user_id :indicators[0], :username :indicators[1], :email :indicators[2];

for (int i = 0; i < 3; i++) {
    if (indicators[i] == -1) {
        printf("Column %d is NULL\n", i);
    }
}

CREATE OR REPLACE FUNCTION get_user_profile(
    user_id_param INTEGER,
    OUT user_name TEXT,
    OUT email TEXT,
    OUT phone TEXT
) AS $$
BEGIN
    SELECT name, email_address, phone_number
    INTO user_name, email, phone
    FROM users
    WHERE id = user_id_param;

    -- If no rows found, all OUT variables are NULL
    -- Client must use indicators to detect this
END;
$$ LANGUAGE plpgsql;

SELECT
  user_id,
  COALESCE(username, 'unknown') as username,
  COALESCE(email, '[email protected]') as email
FROM users
WHERE active = true;

-- In ECPG, this eliminates NULL columns so indicators aren't needed
EXEC SQL SELECT user_id, COALESCE(username, 'unknown'), COALESCE(email, 'no-email')
         INTO :id, :name, :email FROM users;

// Test cursor with nullable data
EXEC SQL DECLARE test_cursor CURSOR FOR
    SELECT id, name, bio FROM users ORDER BY id;

int user_id;
char name[100];
char bio[500];
short name_ind, bio_ind;

EXEC SQL FETCH test_cursor INTO :user_id, :name :name_ind, :bio :bio_ind;

// Verify indicators are properly set
assert(name_ind == 0 || name_ind == -1);
assert(bio_ind == 0 || bio_ind == -1);