MongoDB $lt 运算符2024 年 9 月 6 日 | 3 分钟阅读 MongoDB 中的 $lt 操作符是什么？MongoDB 提供了多种比较查询操作符。 $lt (小于) 操作符是其中之一。 $lt 操作符用于选择字段值小于 (<) 指定值的文档。 您可以根据您的需求在 update、find 等方法中使用此操作符。 $lt 操作符的语法示例在下面的示例中，我们将使用 >db.employee.find()
{
"_id" : 1,
"name" : "John",
"father_name" : "Thomas",
"department" : "Contain Writting",
"experience" : 2,
"mobile_no" : 9856321478,
"gender" : "Male",
"salary" : 22000,
"age" : 26
}
{
"_id" : 2,
"name" : "William",
"father_name" : "Rebort",
"department" : "Softwre Tester",
"experience" : 1,
"mobile_no" : 7896541478,
"gender" : "Male",
"salary" : 20000,
"age" : 21
}
{
"_id" : 3,
"name" : "Ava",
"father_name" : "William",
"department" : "Marketing manager",
"experience" : 5,
"mobile_no" : 8789654178,
"gender" : "Female",
"salary" : 36500,
"age" : 25
}
{
"_id" : 4,
"name" : "Olivia",
"father_name" : "Noah",
"department" : null,
"experience" : 4,
"mobile_no" : 9045641478,
"gender" : "Female",
"salary" : 30000,
"age" : 27
}
{
"_id" : 5,
"name" : "Elijah",
"father_name" : "John",
"department" : "HR",
"experience" : 0,
"mobile_no" : 6589741230,
"gender" : "Male",
"salary" : 15000,
"age" : 20
}
{
"_id" : 6,
"name" : "John",
"father_name" : "Liam",
"department" : "Softwre Tester",
"experience" : 10,
"mobile_no" : 9014536987,
"gender" : "Male",
"salary" : 55000,
"age" : 30
}
示例 1：使用 $lt 操作符 在此示例中，我们正在寻找工资低于 35000 的文档。 输出 {
"_id" : 1,
"name" : "John",
"father_name" : "Thomas",
"department" : "Contain Writting",
"experience" : 2,
"mobile_no" : 9856321478,
"gender" : "Male",
"salary" : 22000,
"age" : 26
}
{
"_id" : 2,
"name" : "William",
"father_name" : "Rebort",
"department" : "Softwre Tester",
"experience" : 1,
"mobile_no" : 7896541478,
"gender" : "Male",
"salary" : 20000,
"age" : 21
}
{
"_id" : 4,
"name" : "Olivia",
"father_name" : "Noah",
"department" : null,
"experience" : 4,
"mobile_no" : 9045641478,
"gender" : "Female",
"salary" : 30000,
"age" : 27
}
{
"_id" : 5,
"name" : "Elijah",
"father_name" : "John",
"department" : "HR",
"experience" : 0,
"mobile_no" : 6589741230,
"gender" : "Male",
"salary" : 15000,
"age" : 20
}
示例 2：另一个字段 在此示例中，我们正在寻找年龄小于 25 的文档。 输出 {
"_id" : 2,
"name" : "William",
"father_name" : "Rebort",
"department" : "Softwre Tester",
"experience" : 1,
"mobile_no" : 7896541478,
"gender" : "Male",
"salary" : 20000,
"age" : 21
}
{
"_id" : 5,
"name" : "Elijah",
"father_name" : "John",
"department" : "HR",
"experience" : 0,
"mobile_no" : 6589741230,
"gender" : "Male",
"salary" : 15000,
"age" : 20
}
示例 3：使用 $lt 操作符更新值 在此示例中，我们正在更新工作经验少于 3 年的员工的 salary 字段。 输出 {
"_id" : 1,
"name" : "John",
"father_name" : "Thomas",
"department" : "Contain Writting",
"experience" : 2,
"mobile_no" : 9856321478,
"gender" : "Male",
"salary" : 25000,
"age" : 26
}
{
"_id" : 2,
"name" : "William",
"father_name" : "Rebort",
"department" : "Softwre Tester",
"experience" : 1,
"mobile_no" : 7896541478,
"gender" : "Male",
"salary" : 25000,
"age" : 21
}
{
"_id" : 5,
"name" : "Elijah",
"father_name" : "John",
"department" : "HR",
"experience" : 0,
"mobile_no" : 6589741230,
"gender" : "Male",
"salary" : 25000,
"age" : 20
}
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