如何在PostgreSQL中創建交叉表查詢

Question

如何在PostgreSQL中使用交叉表函數，我嘗試了自己的查詢但仍無法正常工作。我有以下表格：

sampling_point time_sampling entero sampling_type 
    wall    06:53   50 Environment 
    floor   09:21   50 Environment 
    wall    09:22   50 Environment 
    wall    09:23   50 Environment 
    floor   06:52   10 Environment 
    wall    06:53   50 Environment 
    floor   06:32   10 Environment 
    wall    06:33   50 Environment 
    floor   06:32   50 Environment 
    wall    06:33   50 Environment 
    floor   06:52   50 Environment 
    floor   09:22   50 Environment 

，我想創建查詢返回以下交叉：

sampling_point time_sampling entero_floor entero_wall 
    wall    06:53       50  
    wall    09:22       50  
    wall    09:23       50  
    wall    06:53       50  
    wall    06:33       50  
    wall    06:33       50  
    floor   09:21   50      
    floor   06:52   10      
    floor   06:32   10      
    floor   06:32   50 
    floor   06:52   50 
    floor   09:22   50 

我使用交叉（）有兩個參數是這樣的：

SELECT * FROM crosstab 
    (
     'SELECT c.sampling_date, c.sampling_point, c.time_sampling, c.ha_entero 
     FROM (select t066dtl.*, t066hdr.* from tblfrmintqad066dtl t066dtl 
         JOIN tblfrmintqad066hdr t066hdr ON t066hdr.headerid = t066dtl.headerid AND t066dtl.status= 1) c 
     ORDER BY 1,2', 
      $$VALUES ('floor'::text),('wall'::text)$$ 
    ) 
    AS ct (sampling_point varchar, floor varchar, wall varchar) c.sampling_date = '2016-05-12'; 

在此先感謝。

Answer 1

只需使用CASE WHEN條件表達式：

SELECT sampling_point, time_sampling, 
     CASE WHEN sampling_point = 'floor' THEN entero ELSE NULL END AS entero_floor, 
     CASE WHEN sampling_point = 'wall' THEN entero ELSE NULL END AS entero_wall 
FROM SourceTable 
ORDER BY sampling_point DESC;