实现SQL Server 原生数据从XML生成JSON数据的实例代码

   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:

实现SQL Server 原生数据从XML生成JSON数据的实例代码

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>   </station>   

3.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   END   

  CREATE 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+'"'   end   

3)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"}]}]}]   

总结:

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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