续集连接两个不相关的表

本教程将介绍续集连接两个不相关的表的处理方法,这篇教程是从别的地方看到的,然后加了一些国外程序员的疑问与解答,希望能对你有所帮助,好了,下面开始学习吧。

续集连接两个不相关的表 教程 第1张

问题描述

我正在尝试通过使用关系连接两个未关联"的表来检索数据.这两个表如下:

mysql> desc partner_txns;
+------------+-------------+------+-----+---------+----------------+
| Field| Type  | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+----------------+
| id| int(11)  | NO| PRI | NULL | auto_increment |
| txn_id  | int(11)  | NO|  | NULL | |
| user_id | int(11)  | NO| MUL | NULL | |
| txn_type| varchar(1)  | YES  |  | NULL | |
| txn_amnt| double| YES  |  | NULL | |
| desc | varchar(64) | YES  |  | NULL | |
| createdBy  | int(11)  | NO| MUL | NULL | |
| created_on | datetime | NO|  | NULL | |
+------------+-------------+------+-----+---------+----------------+
8 rows in set (0.00 sec)

mysql> desc accounts_master;
+-------------+-------------+------+-----+---------+----------------+
| Field | Type  | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+----------------+
| id | int(11)  | NO| PRI | NULL | auto_increment |
| name  | varchar(64) | NO|  | NULL | |
| owner | int(11)  | NO| MUL | NULL | |
| type  | int(11)  | YES  |  | 0 | |
| expires_on  | datetime | NO|  | NULL | |
| max_lists| int(11)  | YES  |  | 10| |
| max_groups  | int(11)  | YES  |  | 10| |
| createdBy| int(11)  | NO| MUL | NULL | |
| modifiedBy  | int(11)  | NO| MUL | NULL | |
| created_on  | datetime | NO|  | NULL | |
| modified_on | datetime | NO|  | NULL | |
+-------------+-------------+------+-----+---------+----------------+
11 rows in set (0.00 sec)

如果不使用 sequelize,通常我会像这样进行 SQL 查询:

mysql> select a.user_id, b.name from partner_txns a, accounts_master b where a.createdBy = 3 and a.user_id = b.owner;
+---------+-------------+
| user_id | name  |
+---------+-------------+
| 8 | New account |
| 8 | Comviva  |
| 8 | Infosys  |
| 9 | HDFC  |
| 9 | INTEGRA  |
+---------+-------------+
5 rows in set (0.00 sec)

假设我将这两个表作为两个模型如下:

PartnerTxn

帐户

我很想像这样使用:

var Model = require('ecp_model');

Model.PartnerTxn.findAll({
  where: {createdBy:3 },
  include : [{model:Model.Account, attribute:['name']}]
}).then(function(results) {
console.log("results:", results);
});
[rv.nath@localhost authserver]$ 

但是这将不起作用,因为这两个表不相关.所以,我收到如下错误:

Unhandled rejection Error: Account is not associated to PartnerTxn!
 at validateIncludedElement (/var/opt/ecp_db/node_modules/sequelize/lib/model.js:569:11)
 at /var/opt/ecp_db/node_modules/sequelize/lib/model.js:452:29
 at Array.map (native)
 at validateIncludedElements (/var/opt/ecp_db/node_modules/sequelize/lib/model.js:448:37)
 at null.<anonymous> (/var/opt/ecp_db/node_modules/sequelize/lib/model.js:1360:32)
 at tryCatcher (/var/opt/ecp_db/node_modules/bluebird/js/release/util.js:16:23)
 at Promise._settlePromiseFromHandler (/var/opt/ecp_db/node_modules/bluebird/js/release/promise.js:503:31)
 at Promise._settlePromise (/var/opt/ecp_db/node_modules/bluebird/js/release/promise.js:560:18)
 at Promise._settlePromise0 (/var/opt/ecp_db/node_modules/bluebird/js/release/promise.js:605:10)
 at Promise._settlePromises (/var/opt/ecp_db/node_modules/bluebird/js/release/promise.js:684:18)
 at Async._drainQueue (/var/opt/ecp_db/node_modules/bluebird/js/release/async.js:126:16)
 at Async._drainQueues (/var/opt/ecp_db/node_modules/bluebird/js/release/async.js:136:10)
 at Immediate.Async.drainQueues [as _onImmediate] (/var/opt/ecp_db/node_modules/bluebird/js/release/async.js:16:14)
 at processImmediate [as _immediateCallback] (timers.js:383:17)

推荐答案

我知道这已经快一年了,但万一有人遇到你的情况并寻找正确答案.

当您有两个单独的数据类型通过第三个表链接时,您正在寻找 Sequelize 的 BelongToMany(Through).

因此,在您的情况下,您需要定义第三个模型:UserMaster.请问给 UserMaster 两个属性:user_id(与 PartnerTxn 属性相同)和 owner(与 Account 属性相同).

然后你会这样做:

Account.belongsToMany(PartnerTxn, {through: 'UserMaster'});
PartnerTxn.belongsToMany(Account, {through: 'UserMaster'});

如需进一步参考,文档 有信息.

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