SQL command failed on the page execution - php

Question

Just tested SQL command on phpmyadmin,it is successful.
But in the pages of php code, it is still an error occurred.
The error：
Erreur de syntaxe près de 'SELECT * FROM memberdata='david'' à la ligne 1
My connSQL php code：
<?php
$hostname_connSQL = "localhost";
$database_connSQL = "member";
$username_connSQL = "root";
$password_connSQL = "pooleasee";
$connSQL = mysqli_connect($hostname_connSQL, $username_connSQL, $password_connSQL) or die('Error：' .mysqli_error($connSQL));
mysqli_query($connSQL,"SET NAMES utf8")
?>
My login php code：
<?php
header("Content-Type: text/html; charset=utf-8");
require_once("connSQL.php");
session_start();
if(isset($_SESSION["m_username"]) && ($_SESSION["m_username"]!=""))
{
header("Location: membercenter.php");
}
if(isset($_POST["m_username"]) && isset($_POST["m_password"]))
{
$sql = "USE `member`; SELECT * FROM `memberdata`='".$_POST["m_username"]."'";
$RecLogin = mysqli_query($connSQL,$sql)or die('Error：' .mysqli_error($connSQL));
}
$row_RecLogin = mysqli_fetch_assoc($RecLogin);
$m_username = $row_RecLogin["m_username"];
$m_password = $row_RecLogin["m_password"];
if($_POST["m_password"]==$m_password)
{
$_SESSION["m_username"] = $m_username;
if(isset($_POST["rememberme"]) && ($_POST["rememberme"]=="true"))
{
setcookie("m_username", $_POST["m_username"], time()+365*24*60*60);
setcookie("m_password", $_POST["m_password"], time()+365*24*60*60);
} else
{
if(isset($_COOKIE["m_username"]))
{
setcookie("m_username", $_POST["m_username"], time()-100);
setcookie("m_password", $_POST["m_password"], time()-100);
}
}
{
header("Location: membercenter.php");
}
}
else
{
header("Location: index.php?loginFail=true");
}
?>
My database：
Actually I am a tiro,there are many places to learn.I couldn't find error.I hope you can help me.

Answer 1

Your query syntax is incorrect, WHERE columnName is missing. Also always escape the value with mysqli_real_escape_string
Incorrect Syntax:
$sql = "SELECT * FROM `memberdata`='".$_POST["m_username"]."'";
Correct Syntax:
$sql = "SELECT * FROM `memberdata` WHERE m_username='".mysqli_real_escape_string($connSQL, $_POST["m_username"])."'";

Answer 2

Change sql syntax to
$sql = "SELECT * FROM memberdata WHERE `m_username`='" . $_POST["m_username"] . "'";