MongoDB（10）- 查詢嵌套文檔

插入測試數據

db.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" }
]);

后面的栗子都會用到這里的測試數據

 

精確匹配嵌套文檔

> db.inventory.find( { size: { h: 14, w: 21, uom: "cm" } } )
{ "_id" : ObjectId("60b5e622dd6e93ee8bf35a9d"), "item" : "journal", "qty" : 25, "size" : { "h" : 14, "w" : 21, "uom" : "cm" }, "status" : "A" }

這種寫法不僅需要嵌套文檔的字段、值相同，字段順序也得一致

db.inventory.find(  { size: { w: 21, h: 14, uom: "cm" } }  )

換了個字段順序就查不到同一條文檔了

 

查詢嵌套字段

要在嵌入/嵌套文檔中的字段上指定查詢條件，語法格式如下

"field.nestedField"

跟 JSON 取值一樣，用 . 來找下一級的字段

 

栗子一：嵌套字段等於操作

> db.inventory.find( { "size.uom": "in" } )
{ "_id" : ObjectId("60b5e622dd6e93ee8bf35a9e"), "item" : "notebook", "qty" : 50, "size" : { "h" : 8.5, "w" : 11, "uom" : "in" }, "status" : "A" }
{ "_id" : ObjectId("60b5e622dd6e93ee8bf35a9f"), "item" : "paper", "qty" : 100, "size" : { "h" : 8.5, "w" : 11, "uom" : "in" }, "status" : "D" } 

size 字段值是一個文檔，找到嵌套文檔的 h 字段值等於 in 的所有文檔

 

栗子二：嵌套字段結合單個查詢條件操作符

> db.inventory.find( { "size.h": { $lt: 15 } } )
{ "_id" : ObjectId("60b5e622dd6e93ee8bf35a9d"), "item" : "journal", "qty" : 25, "size" : { "h" : 14, "w" : 21, "uom" : "cm" }, "status" : "A" }
{ "_id" : ObjectId("60b5e622dd6e93ee8bf35a9e"), "item" : "notebook", "qty" : 50, "size" : { "h" : 8.5, "w" : 11, "uom" : "in" }, "status" : "A" }
{ "_id" : ObjectId("60b5e622dd6e93ee8bf35a9f"), "item" : "paper", "qty" : 100, "size" : { "h" : 8.5, "w" : 11, "uom" : "in" }, "status" : "D" }
{ "_id" : ObjectId("60b5e622dd6e93ee8bf35aa1"), "item" : "postcard", "qty" : 45, "size" : { "h" : 10, "w" : 15.25, "uom" : "cm" }, "status" : "A" }

size 字段值是一個文檔，找到嵌套文檔的 h 字段值小於 15 的所有文檔

 

栗子三：多個不同嵌套字段結合 and 操作

> db.inventory.find( { "size.h": { $lt: 15 }, "size.uom": "in", status: "D" } )
{ "_id" : ObjectId("60b5e622dd6e93ee8bf35a9f"), "item" : "paper", "qty" : 100, "size" : { "h" : 8.5, "w" : 11, "uom" : "in" }, "status" : "D" }

三個條件必須同時滿足

• size 字段，嵌套文檔的 h 字段值小於 15
• size 字段，嵌套文檔的 uom 字段值等於 in
• status 字段值等於 D

 

重點

如果是指定單個字段的時候，可以不需要加 ""（當然，加了也無妨），比如

db.inventory.find( { status: "D" } )

 

如果是指定嵌套字段，必須加 "" ，比如上面的栗子

db.inventory.find( { "size.uom": "in" } )