Lua中的返回值

function SearchDatabase(ply, value)
    local id = ply:SteamID()
    if id == nil then return end
    local query = ECLIPSEUSERDATA:query("SELECT " .. value .. " FROM main WHERE usersteamid = '" .. id .. "';")
    if not query then return end
    query.onData = function(q, d)
        if(#query:getData() >= 1)then
            print("[SQL]" .. value .. " = " .. tostring(d[value]))
            print(tostring(d[value]))
            return tostring(d[value])
        end
    end
    query.onError = function(db, err)
        print("[SQL] 数据库搜索失败 - 错误信息: ", err)
    end
    query:start()
    query:wait()
end

function UpdatePlaytime(ply)
    if ply == nil then
        return
    end
    local PlayersPlaytime = SearchDatabase(ply, "playtime")
    print(PlayersPlaytime)
    local PlaytimeUpdate = PlayersPlaytime + 1
end

目前我遇到的问题是，当值: d[value]，被返回到我的函数UpdatePlaytime()时，它会返回一个空值，我不知道如何解决它。

控制台日志:

[SQL]playtime = 0
0
nil

感谢任何帮助！

-D12