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实现 SQL Server 原生数据从 XML 生成 JSON 数据的实例代码怎么编写
实现 SQL Server 原生数据从 XML 生成 JSON 数据的实例代码怎么编写，很多新手对此不是很清楚，为了帮助大家解决这个难题，下面丸趣 TV 小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。
实现 SQL Server 原生数据从 XML 生成 JSON 数据的实例代码
SQL Server 是关系数据库，查询结果通常都是数据集，但是在一些特殊需求下，我们需要 XML 数据，最近这些年，JSON 作为 WebAPI 常用的交换数据格式，那么数据库如何生成 JSON 数据呢？今天就写了一个 DEMO.
1. 创建表及测试数据
SET NOCOUNT ON IF OBJECT_ID(STATS) IS NOT NULL DROP TABLE STATS IF OBJECT_ID(STATIONS) IS NOT NULL DROP TABLE STATIONS IF OBJECT_ID(OPERATORS) IS NOT NULL DROP TABLE OPERATORS IF OBJECT_ID(REVIEWS) IS NOT NULL DROP TABLE REVIEWS -- Create and populate table with Station CREATE TABLE STATIONS(ID INTEGER PRIMARY KEY, CITY NVARCHAR(20), STATE CHAR(2), LAT_N REAL, LONG_W REAL); INSERT INTO STATIONS VALUES (13, Phoenix , AZ , 33, 112); INSERT INTO STATIONS VALUES (44, Denver , CO , 40, 105); INSERT INTO STATIONS VALUES (66, Caribou , ME , 47, 68); -- Create and populate table with Operators CREATE TABLE OPERATORS(ID INTEGER PRIMARY KEY, NAME NVARCHAR(20), SURNAME NVARCHAR(20)); INSERT INTO OPERATORS VALUES (50, John The Fox , Brown INSERT INTO OPERATORS VALUES (51, Paul , Smith INSERT INTO OPERATORS VALUES (52, Michael , Williams -- Create and populate table with normalized temperature and precipitation data CREATE TABLE STATS ( STATION_ID INTEGER REFERENCES STATIONS(ID), MONTH INTEGER CHECK (MONTH BETWEEN 1 AND 12), TEMP_F REAL CHECK (TEMP_F BETWEEN -80 AND 150), RAIN_I REAL CHECK (RAIN_I BETWEEN 0 AND 100), PRIMARY KEY (STATION_ID, MONTH)); INSERT INTO STATS VALUES (13, 1, 57.4, 0.31); INSERT INTO STATS VALUES (13, 7, 91.7, 5.15); INSERT INTO STATS VALUES (44, 1, 27.3, 0.18); INSERT INTO STATS VALUES (44, 7, 74.8, 2.11); INSERT INTO STATS VALUES (66, 1, 6.7, 2.10); INSERT INTO STATS VALUES (66, 7, 65.8, 4.52); -- Create and populate table with Review CREATE TABLE REVIEWS(STATION_ID INTEGER,STAT_MONTH INTEGER,OPERATOR_ID INTEGER) insert into REVIEWS VALUES (13,1,50) insert into REVIEWS VALUES (13,7,50) insert into REVIEWS VALUES (44,7,51) insert into REVIEWS VALUES (44,7,52) insert into REVIEWS VALUES (44,7,50) insert into REVIEWS VALUES (66,1,51) insert into REVIEWS VALUES (66,7,51)2. 查询结果集
select STATIONS.ID as ID, STATIONS.CITY as City, STATIONS.STATE as State, STATIONS.LAT_N as LatN, STATIONS.LONG_W as LongW, STATS.MONTH as Month, STATS.RAIN_I as Rain, STATS.TEMP_F as Temp, OPERATORS.NAME as Name, OPERATORS.SURNAME as Surname from stations inner join stats on stats.STATION_ID=STATIONS.ID left join reviews on reviews.STATION_ID=stations.id and reviews.STAT_MONTH=STATS.[MONTH] left join OPERATORS on OPERATORS.ID=reviews.OPERATOR_ID结果：
2. 查询 xml 数据
select stations.*, (select stats.*, (select OPERATORS.* from OPERATORS inner join reviews on OPERATORS.ID=reviews.OPERATOR_ID where reviews.STATION_ID=STATS.STATION_ID and reviews.STAT_MONTH=STATS.MONTH for xml path( operator),type ) operators from STATS where STATS.STATION_ID=stations.ID for xml path(stat),type ) stats from stations for xml path(station),type结果：
station ID 13 /ID CITY Phoenix /CITY STATE AZ /STATE LAT_N 3.3000000e+001 /LAT_N LONG_W 1.1200000e+002 /LONG_W stats stat STATION_ID 13 /STATION_ID MONTH 1 /MONTH TEMP_F 5.7400002e+001 /TEMP_F RAIN_I 3.1000000e-001 /RAIN_I operators operator ID 50 /ID NAME John The Fox /NAME SURNAME Brown /SURNAME /operator /operators /stat stat STATION_ID 13 /STATION_ID MONTH 7 /MONTH TEMP_F 9.1699997e+001 /TEMP_F RAIN_I 5.1500001e+000 /RAIN_I operators operator ID 50 /ID NAME John The Fox /NAME SURNAME Brown /SURNAME /operator /operators /stat /stats /station station ID 44 /ID CITY Denver /CITY STATE CO /STATE LAT_N 4.0000000e+001 /LAT_N LONG_W 1.0500000e+002 /LONG_W stats stat STATION_ID 44 /STATION_ID MONTH 1 /MONTH TEMP_F 2.7299999e+001 /TEMP_F RAIN_I 1.8000001e-001 /RAIN_I /stat stat STATION_ID 44 /STATION_ID MONTH 7 /MONTH TEMP_F 7.4800003e+001 /TEMP_F RAIN_I 2.1099999e+000 /RAIN_I operators operator ID 51 /ID NAME Paul /NAME SURNAME Smith /SURNAME /operator operator ID 52 /ID NAME Michael /NAME SURNAME Williams /SURNAME /operator operator ID 50 /ID NAME John The Fox /NAME SURNAME Brown /SURNAME /operator /operators /stat /stats /station station ID 66 /ID CITY Caribou /CITY STATE ME /STATE LAT_N 4.7000000e+001 /LAT_N LONG_W 6.8000000e+001 /LONG_W stats stat STATION_ID 66 /STATION_ID MONTH 1 /MONTH TEMP_F 6.6999998e+000 /TEMP_F RAIN_I 2.0999999e+000 /RAIN_I operators operator ID 51 /ID NAME Paul /NAME SURNAME Smith /SURNAME /operator /operators /stat stat STATION_ID 66 /STATION_ID MONTH 7 /MONTH TEMP_F 6.5800003e+001 /TEMP_F RAIN_I 4.5200000e+000 /RAIN_I operators operator ID 51 /ID NAME Paul /NAME SURNAME Smith /SURNAME /operator /operators /stat /stats /station3. 如何生成 JSON 数据
1）创建辅助函数
CREATE FUNCTION [dbo].[qfn_XmlToJson](@XmlData xml) RETURNS nvarchar(max) AS BEGIN declare @m nvarchar(max) SELECT @m= [+Stuff ( (SELECT theline from (SELECT , + { +Stuff ( (SELECT , +coalesce(b.c.value( local-name(.) , NVARCHAR(255) ), )+ : + case when b.c.value(count(*) , int )=0 then dbo.[qfn_JsonEscape](b.c.value( text()[1] , NVARCHAR(MAX) )) else dbo.qfn_XmlToJson(b.c.query( *)) end from x.a.nodes(*) b(c) for xml path(),TYPE).value((./text())[1] , NVARCHAR(MAX) ) ,1,1, )+ } from @XmlData.nodes(/*) x(a) ) JSON(theLine) for xml path(),TYPE).value(. , NVARCHAR(MAX) ) ,1,1, )+ ] return @m ENDCREATE FUNCTION [dbo].[qfn_JsonEscape](@value nvarchar(max) ) returns nvarchar(max) as begin if (@value is null) return null if (TRY_PARSE( @value as float) is not null) return @value set @value=replace(@value, \ , \\) set @value=replace(@value, , \) return +@value+ end3）查询 sql
select dbo.qfn_XmlToJson ( ( select stations.ID,stations.CITY,stations.STATE,stations.LAT_N,stations.LONG_W , (select stats.*, (select OPERATORS.* from OPERATORS inner join reviews on OPERATORS.ID=reviews.OPERATOR_ID where reviews.STATION_ID=STATS.STATION_ID and reviews.STAT_MONTH=STATS.MONTH for xml path( operator),type ) operators from STATS where STATS.STATION_ID=stations.ID for xml path(stat),type ) stats from stations for xml path(stations),type ) )结果：
[ { ID :13, CITY : Phoenix , STATE : AZ , LAT_N :3.3000000e+001, LONG_W :1.1200000e+002, stats :[ { STATION_ID :13, MONTH :1, TEMP_F :5.7400002e+001, RAIN_I :3.1000000e-001, operators :[ { ID :50, NAME : John \ The Fox\ , SURNAME : Brown}]}, {STATION_ID :13, MONTH :7, TEMP_F :9.1699997e+001, RAIN_I :5.1500001e+000, operators :[ { ID :50, NAME : John \ The Fox\ , SURNAME : Brown}]}]}, {ID :44, CITY : Denver , STATE : CO , LAT_N :4.0000000e+001, LONG_W :1.0500000e+002, stats :[ { STATION_ID :44, MONTH :1, TEMP_F :2.7299999e+001, RAIN_I :1.8000001e-001}, {STATION_ID :44, MONTH :7, TEMP_F :7.4800003e+001, RAIN_I :2.1099999e+000, operators :[ { ID :51, NAME : Paul , SURNAME : Smith}, {ID :52, NAME : Michael , SURNAME : Williams}, {ID :50, NAME : John \ The Fox\ , SURNAME : Brown}]}]}, {ID :66, CITY : Caribou , STATE : ME , LAT_N :4.7000000e+001, LONG_W :6.8000000e+001, stats :[ { STATION_ID :66, MONTH :1, TEMP_F :6.6999998e+000, RAIN_I :2.0999999e+000, operators :[ { ID :51, NAME : Paul , SURNAME : Smith}]}, {STATION_ID :66, MONTH :7, TEMP_F :6.5800003e+001, RAIN_I :4.5200000e+000, operators :[ { ID :51, NAME : Paul , SURNAME : Smith}]}]}]JSON 作为灵活的 Web 通信交换架构，如果把配置数据存放在数据库中，直接获取 JSON，那配置就会非常简单了，也能够大量减轻应用服务器的压力！
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