如果某些文档中的字段为null,如何在对字段使用$ dateFromString时避免结果为空字段。
Mongo Playground-结果中的日期字段不应为空
文档:
[
{
"date1": ISODate("2019-05-20T19:04:35.000Z")
},
{
"date1": ISODate("2019-05-20T19:04:35.000Z"),
"date2": ISODate("2019-05-20T19:04:35.000Z")
},
{
"date3": ISODate("2019-05-20T19:04:35.000Z")
}
]
预期:
[
{
"date1": ISODate("2019-05-20T00:00:00Z")
},
{
"date1": ISODate("2019-05-20T00:00:00Z"),
"date2": ISODate("2019-05-20T00:00:00Z")
},
{
"date3": ISODate("2019-05-20T00:00:00Z")
}
]
答案 0 :(得分:2)
您可以使用$type
检查日期是否为空或缺少日期,如果缺少日期,请使用$$REMOVE
删除
db.collection.aggregate([
{
$project: {
date1: {
$cond: {
if: {
$or: [
{ $eq: [{ $type: "$date1" }, "missing"] },
{ $eq: ["$date1", null] }
]
},
then: "$$REMOVE",
else: {
$dateFromString: {
dateString: {
$dateToString: {
format: "%Y-%m-%d",
date: "$date1"
}
}
}
}
}
},
date2: {
$cond: {
if: {
$or: [
{ $eq: [{ $type: "$date2" }, "missing"] },
{ $eq: ["$date2", null] }
]
},
then: "$$REMOVE",
else: {
$dateFromString: {
dateString: {
$dateToString: {
format: "%Y-%m-%d",
date: "$date2"
}
}
}
}
}
},
date3: {
$cond: {
if: {
$or: [
{ $eq: [{ $type: "$date3" }, "missing"] },
{ $eq: ["$date3", null] }
]
},
then: "$$REMOVE",
else: {
$dateFromString: {
dateString: {
$dateToString: {
format: "%Y-%m-%d",
date: "$date3"
}
}
}
}
}
}
}
}
])