$lt¶

$lt¶

Syntax: {field: {$lt: value} }

$lt selects the documents where the value of the field is less than (i.e. <) the specified value.选择field值小于（即<）指定value的文档。

For most data types, comparison operators only perform comparisons on fields where the BSON type matches the query value’s type. 对于大多数数据类型，比较运算符仅对BSON类型与查询值类型匹配的字段执行比较。MongoDB supports limited cross-BSON comparison through Type Bracketing.MongoDB通过类型括号支持有限的交叉BSON比较。

Consider the following example:考虑下面的例子：

db.inventory.find( { qty: { $lt: 20 } } )

This query will select all documents in the inventory collection where the qty field value is less than 20.此查询将选择inventory集合中qty字段值小于20的所有单据。

Consider the following example which uses the $lt operator with a field from an embedded document:考虑下面的示例，该示例使用$lt运算符和来自嵌入文档的字段：

db.inventory.update( { "carrier.fee": { $lt: 20 } }, { $set: { price: 9.99 } } )

This update() operation will set the price field value in the documents that contain the embedded document carrier whose fee field value is less than 20.此update()操作将在包含fee字段值小于20的嵌入式文档carrier的文档中设置price字段值。

See also参阅

find(), update(), $set.