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實現SQL Server 原生數據從XML生成JSON數據的實例代碼

2024-08-31 01:04:48
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實現SQL Server 原生數據從XML生成JSON數據的實例代碼

   SQL Server 是關系數據庫,查詢結果通常都是數據集,但是在一些特殊需求下,我們需要XML數據,最近這些年,JSON作為WebAPI常用的交換數據格式,那么數據庫如何生成JSON數據呢?今天就寫了一個DEMO.

       1.創建表及測試數據

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.查詢結果集

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 

結果:

SQL,Server,XML生成JSON數據,詳解SQL,原生數據從XML生成JSON數據

2.查詢xml數據

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 

結果:

<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數據

1)創建輔助函數

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)查詢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   ) ) 

結果:

[ {"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"}]}]}] 

總結:

JSON作為靈活的Web通信交換架構,如果把配置數據存放在數據庫中,直接獲取JSON,那配置就會非常簡單了,也能夠大量減輕應用服務器的壓力!

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