检查column是否存在，如果不存在，则通过PHP添加MySQL - Check if column exists, if not, add in MySQL through PHP

Check if column exists, if not, add in MySQL through PHP

我使用以下代码检查列是否存在，如果不存在，则添加它:

mysql_query("select $column from $table") or mysql_query("alter table $table add $column varchar (20)");

但是数据库没有变化。有什么建议吗?

注:数据库已连接

您可以将SQL更改为…

//THIS IS BETTER BUT DONT USE THIS
$qry = "ALTER IGNORE TABLE {$table} ADD {$column} VARCHAR(20);"

使用PHP PDO或MySQLi与准备语句。

MySQLi解决方案:

$mysqli = new mysqli($cfg->host, $cfg->user, $cfg->password, $cfg->db);
if ($mysqli->connect_errno) {
    echo 'Connect failed: ', $mysqli->connect_error, '" }';
    exit();
}
if ($stmt = $mysqli->prepare("ALTER IGNORE TABLE ? ADD ? VARCHAR(20);")) {
    $stmt->bind_param("ss", $table, $column);
    $stmt->execute();
    $stmt->close();
}
$mysqli->close();

$r=mysql_num_rows(mysql_query("SHOW columns from '".$table."' where field='".$column."'"));
if ($r==0){
    mysql_query("alter table $table add $column varchar (20)");
}

msqli用户

$result = $mysqli->query("SHOW COLUMNS FROM tablename LIKE 'keyword");
$exists = (mysqli_num_rows($result))?TRUE:FALSE;