楼主先要搞清楚,text和longtext这些都是可变长度的字段类型.

这是phpMyAdmin里的说明:

text: 最多存储65535(2^16-1)字节的文本字段,存储时在内容前使用2字节表示内容的字节数.

longtext: 最多存储4294967295字节即4GB(2^32-1)的文本字段,存储时在内容前使用4字节表示内容的字节数.

也就是说,你在longtext类型的字段里只存1个字符,占用空间只不过是4个字节加上1个字符占用的字节数,而不是占用4个GB的存储空间,4个GB指的是该字段能容纳的最大值.

最后就是有明显关系并且需要查询统计的多个量,不建议全部塞到一个字段里面.像不确定的会话数据(如JSON串)这类东西,倒是可以一股脑存到一个longtext字段.比如我的会话表:

DROP TABLE IF EXISTS `io_session`;

CREATE TABLE IF NOT EXISTS `io_session` (

`user_id` bigint unsigned NOT NULL COMMENT ‘用户编号’,

`data` longtext NOT NULL COMMENT ‘会话内容’,

`create_time` bigint unsigned NOT NULL COMMENT ‘创建时间’,

`update_time` bigint unsigned NOT NULL COMMENT ‘更新时间’,

`version` smallint unsigned NOT NULL DEFAULT ‘0’ COMMENT ‘版本号’,

`flag` tinyint NOT NULL DEFAULT ‘1’ COMMENT ‘版本号递增递减方向标识’,

PRIMARY KEY (`user_id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci COMMENT=’会话表’;

// 填出会话数据到数组 $io[‘user’][‘session’]

function io_session_get() {

global $io;

if(!isset($io[‘user’][‘id’])) return false;

$db = io_db();

$table = IO_DB_PREFIX.’session’;

$sql = “SELECT * FROM `{$table}` WHERE `user_id` = ?”;

$stmt = $db->prepare($sql); $stmt->execute(array($io[‘user’][‘id’]));

$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

if(!isset($rows[0])) return false;

$data = json_decode($rows[0][‘data’], true);

// JSON解码失败时,把会话内容重置为空

$io[‘user’][‘session’][‘data’] = ($data) ? $data : array();

$io[‘user’][‘session’][‘version’] = $rows[0][‘version’];

$io[‘user’][‘session’][‘flag’] = $rows[0][‘flag’];

//register_shutdown_function(‘io_session_set’);

}

// 将会话数据写入到数据库

function io_session_set() {

global $io;

if(!isset($io[‘user’][‘session’])) return false;

$data = json_encode($io[‘user’][‘session’][‘data’]);

$db = io_db();

$table = IO_DB_PREFIX.’session’;

switch(true) {

// version 类型 smallint 范围 0 到 65535

case ($io[‘user’][‘session’][‘flag’] == 1 && $io[‘user’][‘session’][‘version’] != 65535): {

$sql = “UPDATE `{$table}` SET `data` = ?, `version` = ?

WHERE `user_id` = ? AND `version` = ? AND `flag` = 1″;

$version_increase = true;

break;

}

case ($io[‘user’][‘session’][‘flag’] == 1 && $io[‘user’][‘session’][‘version’] == 65535): {

$sql = “UPDATE `{$table}` SET `data` = ?, `version` = ?, `flag` = -1

WHERE `user_id` = ? AND `version` = ? AND `flag` = 1″;

$version_increase = false;

break;

}

case ($io[‘user’][‘session’][‘flag’] == -1 && $io[‘user’][‘session’][‘version’] != 0): {

$sql = “UPDATE `{$table}` SET `data` = ?, `version` = ?

WHERE `user_id` = ? AND `version` = ? AND `flag` = -1″;

$version_increase = false;

break;

}

case ($io[‘user’][‘session’][‘flag’] == -1 && $io[‘user’][‘session’][‘version’] == 0): {

$sql = “UPDATE `{$table}` SET `data` = ?, `version` = ?, `flag` = 1

WHERE `user_id` = ? AND `version` = ? AND `flag` = -1″;

$version_increase = true;

break;

}

}

$stmt = $db->prepare($sql);

$stmt->execute(array(

$data,

$version_increase ? $io[‘user’][‘session’][‘version’] + 1 : $io[‘user’][‘session’][‘version’] – 1,

$io[‘user’][‘id’],

$io[‘user’][‘session’][‘version’],

));

return ($stmt->rowCount() == 0) ? false : true;

}

io_session_get();

var_export($io[‘user’][‘session’]);

$io[‘user’][‘session’][‘data’][‘date’] = date(‘Y-m-d H:i:s’);

io_session_set();