用Sequelize计算关联条目 [英] Counting associated entries with Sequelize
本文介绍了用Sequelize计算关联条目的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有两个表,locations
和sensors
. sensors
中的每个条目都有一个指向locations
的外键.使用Sequelize,如何从locations
获取所有条目以及与locations
中的每个条目相关的sensors
中的条目总数?
I have two tables, locations
and sensors
. Each entry in sensors
has a foreign key pointing to locations
. Using Sequelize, how do I get all entries from locations
and total count of entries in sensors
that are associated with each entry in locations
?
原始SQL:
SELECT
`locations`.*,
COUNT(`sensors`.`id`) AS `sensorCount`
FROM `locations`
JOIN `sensors` ON `sensors`.`location`=`locations`.`id`;
GROUP BY `locations`.`id`;
型号:
module.exports = function(sequelize, DataTypes) {
var Location = sequelize.define("Location", {
id: {
type: DataTypes.INTEGER.UNSIGNED,
primaryKey: true
},
name: DataTypes.STRING(255)
}, {
classMethods: {
associate: function(models) {
Location.hasMany(models.Sensor, {
foreignKey: "location"
});
}
}
});
return Location;
};
module.exports = function(sequelize, DataTypes) {
var Sensor = sequelize.define("Sensor", {
id: {
type: DataTypes.INTEGER.UNSIGNED,
primaryKey: true
},
name: DataTypes.STRING(255),
type: {
type: DataTypes.INTEGER.UNSIGNED,
references: {
model: "sensor_types",
key: "id"
}
},
location: {
type: DataTypes.INTEGER.UNSIGNED,
references: {
model: "locations",
key: "id"
}
}
}, {
classMethods: {
associate: function(models) {
Sensor.belongsTo(models.Location, {
foreignKey: "location"
});
Sensor.belongsTo(models.SensorType, {
foreignKey: "type"
});
}
}
});
return Sensor;
};
推荐答案
将findAll()
与include()
和sequelize.fn()
用作COUNT
:
Location.findAll({
attributes: {
include: [[Sequelize.fn("COUNT", Sequelize.col("sensors.id")), "sensorCount"]]
},
include: [{
model: Sensor, attributes: []
}]
});
或者,您可能还需要添加group
:
Or, you may need to add a group
as well:
Location.findAll({
attributes: {
include: [[Sequelize.fn("COUNT", Sequelize.col("sensors.id")), "sensorCount"]]
},
include: [{
model: Sensor, attributes: []
}],
group: ['Location.id']
})
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