sql - Does select top 10 * from tablename give same result every time? -


i want know select top 10 * tablename give same result every time?

thanks in advance

no. result set unordered unless specify order by clause. then, order by needs stable, meaning keys have no ties (you accomplish putting primary key last keys ordering).

there several reason why results might differ. obviously, underlying data might change, guessing not gist of question.

the primary reason on multi-threaded machine, different threads reading data. thread returns data indeterminate, don't know first ten rows (without order by).

sql not guarantee tables read in order processing queries. however, in practice, think sql server read pages in order.


Comments

Post a Comment

Popular posts from this blog

user interface - how to replace an ongoing process of image capture from another process call over the same ImageLabel in python's GUI TKinter -

i trying use following code create interactive gui changes color-space(hsv, rbg, grayscale etc) on event of button click. display opencv video in tkinter using multiprocessing being new python having problems multiprocessing , attempts on making gui change it's color space on button clicks hangs entire system. on it's implementation highly appreciated. thankyou. below code: import cv2 pil import image,imagetk import tkinter tk import numpy np multiprocessing import process , queue def quit_it(root,process): root.destroy() process.terminate() def black_andwhite(root,process): process.terminate p=process(target=capture_image, args=(5,queue, )) p.start() root.after(0, func=lambda: update_all(root, image_label, queue)) def update_image(image_label, queue): frame = queue.get() = image.fromarray(frame) b = imagetk.photoimage(image=a) image_label.configure(image=b) image_label._image_cache = b root.update() def update_all(root...
Read more

javascript - Restarting Supervisor and effect on FlaskSocketIO -

in index.html (html/javascript) have: $(document).ready(function(){ namespace = '/test'; var socket = io.connect('http://' + document.domain + ':' + location.port + namespace); socket.on('connect', function() { socket.emit('join', {room: 'venue_1'}); }); socket.on('my response', function(msg) { $('#log').append('<br>received #' + ': ' + msg.data); }); }); on server have: @socketio.on('connect', namespace='/test') def test_connect(): if session.get('venue_id'): emit('my response', {'data': 'connected'}) session.pop('venue_id', none) else: request.namespace.disconnect() @socketio.on('join', namespace='/test') def join(message): join_room(message['room']) room = message[...
Read more

php - Mongodb connectivity error -

<?php /** * connects mongodb server. * stops code execution on`enter code here` connection error. * * not need use file, place globally assign mongodb instance $db. * * define constants in config or here */ define('mdb_username', 'root'); define('mdb_password', 'asd'); define('mdb_host', 'localhost:80'); define('mdb_name', 'abc'); if (!class_exists('mongo')) { die("mongo class not existing. did install php mongodb extension?"); } try { $conn = new mongoclient("mongodb://".mdb_username.":".mdb_password."@".mdb_host."/".mdb_name); $conn->authenticate('root','gynadfehurbo'); $db = $conn->selectdb(mdb_name); } catch (mongoconnectionexception $e) { die($e->getmessage()); // in production might want turn off. } mongodb connectivity problem. while trying connect mongodb php got authentication problem .....
Read more