使用MYSQLI準備多個預處理語句

Question

我剛剛轉到mysqli，我想知道：我可以使用預處理語句執行多個查詢嗎？

下面是示例：我需要檢查此用戶名是否也在表「future_user」中，而不僅僅是在「用戶」中，因爲它現在正在執行。對於代碼上訴，我寧願不再寫相同的功能，只是將「user」改爲「future_user」。

function isFreeUsername($string) 
{ 
$DB = databaseConnect(); 

$stmt = $DB->prepare("SELECT * FROM user WHERE username=? LIMIT 1"); 
$stmt->bind_param("s", $username); 

if(isset($_SESSION) && isset($_GET['username'])) $username = $_GET['username']; 
else            $username = $string; 

$stmt->execute(); 
$stmt->store_result(); 

if($stmt->num_rows > 0) $return = 0; 
else      $return = 1; 

$stmt->close(); 
$DB->close(); 

return $return; 

}

表：

CREATE TABLE user 
(
uid  mediumint(6) unsigned NOT NULL AUTO_INCREMENT PRIMARY KEY, 

username varchar(15) NOT NULL, 
password varchar(15) BINARY NOT NULL, 
mail  varchar(50) NOT NULL, 

name  varchar(50) NOT NULL, 
surname varchar(50) NOT NULL, 
birth char(10) NOT NULL, 
sex  tinyint(1) unsigned NOT NULL default 1, 

address varchar(50) NOT NULL, 
city  varchar(50) NOT NULL, 
zip  char(5) NOT NULL, 
province varchar(50) NOT NULL, 
country tinyint(3) NOT NULL, 

number1 varchar(50) NOT NULL, 
number2 varchar(50) NOT NULL, 

last_login TIMESTAMP,  
registered TIMESTAMP, 
online  tinyint(1) unsigned default 0, 

admin   tinyint(1) unsigned default 0, 
comment_allowed tinyint(1) unsigned default 0, 
post_allowed tinyint(1) unsigned default 0 

) ENGINE=InnoDB; 

CREATE TABLE future_user 
(
username varchar(15) NOT NULL, 
password varchar(15) BINARY NOT NULL, 
mail  varchar(50) NOT NULL, 

name  varchar(50) NOT NULL, 
surname varchar(50) NOT NULL, 
birth char(8) NOT NULL, 
sex  tinyint(1) unsigned NOT NULL, 

address varchar(50) NOT NULL, 
city  varchar(50) NOT NULL, 
zip  char(10) NOT NULL, 
province varchar(50) NOT NULL, 
country varchar(50) NOT NULL, 

number1 varchar(50) NOT NULL, 
number2 varchar(50) NOT NULL, 

code  char(10) NOT NULL 

) ENGINE=InnoDB; 

Answer 1

"SELECT * 
FROM user u 
LEFT JOIN future_user fu on fu.id = u.id 
WHERE u.username=? 
LIMIT 1" 

無法看到更多的表結構，這是我能想出來的。 這將在未來的用戶中選擇用戶

Answer 2

你可以做CROSS JOIN連接兩個表，並詢問他們的方式

SELECT * FROM user JOIN future_user 
    WHERE user.username = ? OR future_user.username = ? 

你可能需要調整*，以便兩個表中名稱相同的列不會相互重疊。