[brianrestup]

PHP Code:

CMD:changename(playerid, params[]) {
    if(isnull(params)) {
        return SendClientMessage(playerid, -1, "/changename [newname]");
    }
    if(strlen(params) > MAX_PLAYER_NAME) {
        return SendClientMessage(playerid, -1, "Your name must contain a maximum of 24 characters.");
    }
    new current[MAX_PLAYER_NAME];
    GetPlayerName(playerid, current, sizeof current);
    if(!strcmp(current, params, false)) {
        return SendClientMessage(playerid, -1, "That's already your name!");
    }
    new query[128];
    mysql_format(handle, query, sizeof query, "SELECT * FROM `users` WHERE `name` = '%s'", params);
    mysql_tquery(handle, query, "ChangeName", "is", playerid, params);
    return 1;
}
forward ChangeName(playerid, newname[]);
public ChangeName(playerid, newname[]) {
    new current[MAX_PLAYER_NAME];
    GetPlayerName(playerid, current, sizeof current);
    new query[128];
    mysql_format(handle, query, sizeof query, "UPDATE `users` SET `name` = '%s' WHERE `name` = '%s'", newname, current);
    mysql_tquery(handle, query);
    SetPlayerName(playerid, newname);
    return 1;
} 


How to make detect Name Already Exist, and player must try more name?

[SiaReyes]

Code:

 if(cache_num_rows()) return error;

[Calisthenics]

ALWAYS escape input by people to avoid SQL Injection.

Set `name` column as UNIQUE KEY, not only the searching will be faster but it will not continue searching if a row is found because it now knows there will never be duplicates.

In /changename:

pawn Code:

mysql_format(..., "UPDATE IGNORE `users` SET `name` = '%e' WHERE `name` = '%s'", ...);
mysql_tquery(handle, query, "OnPlayerNameChange", "ds", playerid, params);

In `OnPlayerNameChange` callback:

pawn Code:

// without `IGNORE` keyword, it would return error about duplicate key
// `IGNORE` literally ignores the error and does absolutely nothing (0 rows are affected)
// When the row is updated (sets the new name), the affected rows will be 1
if (!cache_affected_rows())
{
    // already registered name, pick a new one
}
else
{
    // SetPlayerName
}

[brianrestup]

Quote:

Originally Posted by SiaReyes Code: if(cache_num_rows()) return error;

thanks for reference

[SiaReyes]

Fore more secure and faster method, I suggest you to use Calisthenics's method.

[MichiCZ]

Will it works like this?

Quote:

if(cache_num_rows() > 0) { return SCM blah blah blah "Someone else is using this name!"); }