Query on Embedded/Nested Documents查询嵌入/嵌套文档
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This page provides examples of query operations on embedded/nested documents using the Collection.find() method in the MongoDB Node.js Driver.本页提供了使用MongoDB Node.js驱动程序中的Collection.find()方法对嵌入/嵌套文档进行查询操作的示例。
The examples on this page use the 此页面上的示例使用inventory collection. inventory集合。Connect to a test database in your MongoDB instance then create the 连接到MongoDB实例中的测试数据库，然后创建inventory collection:inventory集合：
await db.collection('inventory').insertMany([
{
item: 'journal',
qty: 25,
size: { h: 14, w: 21, uom: 'cm' },
status: 'A'
},
{
item: 'notebook',
qty: 50,
size: { h: 8.5, w: 11, uom: 'in' },
status: 'A'
},
{
item: 'paper',
qty: 100,
size: { h: 8.5, w: 11, uom: 'in' },
status: 'D'
},
{
item: 'planner',
qty: 75,
size: { h: 22.85, w: 30, uom: 'cm' },
status: 'D'
},
{
item: 'postcard',
qty: 45,
size: { h: 10, w: 15.25, uom: 'cm' },
status: 'A'
}
]);
Match an Embedded/Nested Document匹配嵌入/嵌套文档
To specify an equality condition on a field that is an embedded/nested document, use the query filter document 若要在作为嵌入/嵌套文档的字段上指定相等条件，请使用查询筛选器文档{ <field>: <value> } where <value> is the document to match.{ <field>: <value> }，其中<value>是要匹配的文档。
For example, the following query selects all documents where the field 例如，以下查询选择字段size equals the document { h: 14, w: 21, uom: "cm" }:size等于文档{ h: 14, w: 21, uom: "cm" }的所有文档：
const cursor = db.collection('inventory').find({
size: { h: 14, w: 21, uom: 'cm' }
});
Equality matches on the whole embedded document require an exact match of the specified 整个嵌入文档上的相等匹配要求与指定的<value> document, including the field order. <value>文档完全匹配，包括字段顺序。For example, the following query does not match any documents in the 例如，以下查询与inventory collection:inventory集合中的任何文档都不匹配：
const cursor = db.collection('inventory').find({
size: { w: 21, h: 14, uom: 'cm' }
});
Query on Nested Field查询嵌套字段
To specify a query condition on fields in an embedded/nested document, use dot notation (若要对嵌入/嵌套文档中的字段指定查询条件，请使用点表示法（"field.nestedField")."field.nestedField"）。
When querying using dot notation, the field and nested field must be inside quotation marks.使用点表示法进行查询时，字段和嵌套字段必须位于引号内。
Specify Equality Match on a Nested Field在嵌套字段上指定相等匹配
The following example selects all documents where the field 以下示例选择嵌套在uom nested in the size field equals "in":size字段中的字段uom等于"in"的所有文档：
const cursor = db.collection('inventory').find({
'size.uom': 'in'
});
Specify Match using Query Operator使用查询运算符指定匹配
A query filter document can use the query operators to specify conditions in the following form:查询筛选文档可以使用查询运算符以以下形式指定条件：
{ <field1>: { <operator1>: <value1> }, ... }
The following query uses the less than operator (以下查询在$lt) on the field h embedded in the size field:size字段中嵌入的字段h上使用小于运算符（$lt）：
const cursor = db.collection('inventory').find({
'size.h': { $lt: 15 }
});
Specify AND Condition指定AND条件
AND ConditionThe following query selects all documents where the nested field 以下查询选择嵌套字段h is less than 15, the nested field uom equals "in", and the status field equals "D":h小于15、嵌套字段uom等于"in"、status字段等于"D"的所有文档：
const cursor = db.collection('inventory').find({
'size.h': { $lt: 15 },
'size.uom': 'in',
status: 'D'
});
Additional Query Tutorials其他查询教程
For additional query examples, see:有关其他查询示例，请参阅：