DocumentDB SQL - 选择子句

Azure门户有一个Query Explorer，它允许我们对DocumentDB数据库运行任何SQL查询.我们将使用查询资源管理器演示查询语言的许多不同功能和特性，从最简单的查询开始.

步骤1 : 打开Azure门户，在数据库刀片中，单击查询资源管理器刀片.

请记住，查询在集合范围内运行，因此查询资源管理器允许我们在此下拉列表中选择集合.我们将它设置为包含三个文档的Families集合.我们在这个例子中考虑这三个文档.

以下是 AndersenFamily 文档.

{    "id": "AndersenFamily",    "lastName": "Andersen",    "parents": [       { "firstName": "Thomas", "relationship":  "father" },       { "firstName": "Mary Kay", "relationship":  "mother" }    ],   "children": [       {          "firstName": "Henriette Thaulow",          "gender": "female",          "grade": 5,          "pets": [ { "givenName": "Fluffy", "type":  "Rabbit" } ]       }    ],      "location": { "state": "WA", "county": "King", "city": "Seattle" },    "isRegistered": true }

以下是 SmithFamily 文件.

{    "id": "SmithFamily",   "parents": [       { "familyName": "Smith", "givenName": "James" },       { "familyName": "Curtis", "givenName": "Helen" }    ],    "children": [       {          "givenName": "Michelle",          "gender": "female",          "grade": 1       },      {          "givenName": "John",          "gender": "male",          "grade": 7,          "pets": [             { "givenName": "Tweetie", "type": "Bird" }          ]       }    ],   "location": {       "state": "NY",       "county": "Queens",       "city": "Forest Hills"    },   "isRegistered": true }

以下是 WakefieldFamily 文档.

{    "id": "WakefieldFamily",    "parents": [       { "familyName": "Wakefield", "givenName": "Robin" },       { "familyName": "Miller", "givenName": "Ben" }    ],    "children": [       {          "familyName": "Merriam",          "givenName": "Jesse",          "gender": "female",          "grade": 6,          "pets": [             { "givenName": "Charlie Brown", "type": "Dog" },             { "givenName": "Tiger", "type": "Cat" },             { "givenName": "Princess", "type": "Cat" }          ]       },       {          "familyName": "Miller",          "givenName": "Lisa",          "gender": "female",          "grade": 3,          "pets": [             { "givenName": "Jake", "type": "Snake" }          ]      }    ],    "location": { "state": "NY", "county": "Manhattan", "city": "NY" },    "isRegistered": false}

使用此简单查询SELECT *打开查询资源管理器FROM c，它只是从中检索所有文档集合.虽然它很简单，但它仍然与关系数据库中的等效查询完全不同.

第2步 : 在关系数据库中，SELECT *表示在DocumentDB中返回所有列.这意味着您希望结果中的每个文档都完全按照存储在数据库中的方式返回.

但是当您选择特定属性和表达式而不是简单地发出SELECT *时，那么您正在为结果中的每个文档投射出您想要的新形状.

步骤3 : 单击"运行"以执行查询并打开结果刀片.

可以看到WakefieldFamily，SmithFamily和AndersonFamily被检索.

以下是 SELECT * FROM检索到的三个文档c 查询.

[    {       "id": "WakefieldFamily",      "parents": [          {             "familyName": "Wakefield",             "givenName": "Robin"          },          {             "familyName": "Miller",             "givenName": "Ben"          }       ],        "children": [          {             "familyName": "Merriam",             "givenName": "Jesse",             "gender": "female",             "grade": 6,             "pets": [                {                   "givenName": "Charlie Brown",                   "type": "Dog"                },               {                   "givenName": "Tiger",                   "type": "Cat"                },               {                   "givenName": "Princess",                   "type": "Cat"                }             ]          },          {             "familyName": "Miller",             "givenName": "Lisa",             "gender": "female",             "grade": 3,             "pets": [                {                   "givenName": "Jake",                  "type": "Snake"                }             ]          }       ],       "location": {          "state": "NY",          "county": "Manhattan",          "city": "NY"       },       "isRegistered": false,       "_rid": "Ic8LAJFujgECAAAAAAAAAA==",       "_ts": 1450541623,       "_self": "dbs/Ic8LAA==/colls/Ic8LAJFujgE=/docs/Ic8LAJFujgECAAAAAAAAAA==/",       "_etag": "00000500-0000-0000-0000-567582370000",       "_attachments": "attachments/"    },    {       "id": "SmithFamily",       "parents": [          {             "familyName": "Smith",             "givenName": "James"          },          {             "familyName": "Curtis",             "givenName": "Helen"          }       ],       "children": [          {             "givenName": "Michelle",             "gender": "female",             "grade": 1          },          {             "givenName": "John",             "gender": "male",             "grade": 7,            "pets": [                {                   "givenName": "Tweetie",                   "type": "Bird"                }             ]          }       ],      "location": {          "state": "NY",          "county": "Queens",          "city": "Forest Hills"       },       "isRegistered": true,       "_rid": "Ic8LAJFujgEDAAAAAAAAAA==",       "_ts": 1450541623,       "_self": "dbs/Ic8LAA==/colls/Ic8LAJFujgE=/docs/Ic8LAJFujgEDAAAAAAAAAA==/",       "_etag": "00000600-0000-0000-0000-567582370000",       "_attachments": "attachments/"    },    {       "id": "AndersenFamily",       "lastName": "Andersen",       "parents": [          {             "firstName": "Thomas",             "relationship": "father"          },         {             "firstName": "Mary Kay",             "relationship": "mother"          }       ],       "children": [          {             "firstName": "Henriette Thaulow",             "gender": "female",             "grade": 5,             "pets": [                 "givenName": "Fluffy",                "type": "Rabbit"             ]          }       ],      "location": {          "state": "WA",          "county": "King",          "city": "Seattle"       },      "isRegistered": true,       "_rid": "Ic8LAJFujgEEAAAAAAAAAA==",       "_ts": 1450541624,       "_self": "dbs/Ic8LAA==/colls/Ic8LAJFujgE=/docs/Ic8LAJFujgEEAAAAAAAAAA==/",       "_etag": "00000700-0000-0000-0000-567582380000",       "_attachments": "attachments/"    }]

但是，这些结果还包括系统生成的属性用下划线字符固定.