Question

我是新来的。

附录一

colorname   Hexa    rgb rgbvalue
Violet  #8B00FF r   139
Violet  #8B00FF g   0
Violet  #8B00FF b   255
Indigo  #4B0082 r   75
Indigo  #4B0082 g   0
Indigo  #4B0082 b   130
Blue    #0000FF r   0
Blue    #0000FF g   0
Blue    #0000FF b   255

如果我在服务器中做一个Pivot

SELECT colorname,hexa,[r], [g], [b]
FROM
(SELECT colorname,hexa,rgb,rgbvalue
    FROM tblPivot) AS TableToBePivoted
PIVOT
(
sum(rgbvalue)
FOR rgb IN ([r], [g], [b])
) AS PivotedTable;

我的产出是一样的。

colorname   hexa    r   g   b
Blue    #0000FF 0   0   255
Indigo  #4B0082 75  0   130
Violet  #8B00FF 139 0   255

如何使用邮政总局?

My attempt is

SELECT *
FROM crosstab
(
     SELECT 
        colorname
        ,hexa
        ,rgb
        ,rgbvalue
    FROM tblPivot 
)AS ct(colorname text, hexa text, rgb text, rgbvalue int);

但出现错误:

ERROR:  function crosstab(unknown) does not exist
LINE 2: FROM crosstab
             ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
********** Error **********
ERROR: function crosstab(unknown) does not exist**

Is there any elegant way of doing so in PostgreSQL (any built in function...) What is the standard practice of doing so ?

Answer 1

这可以作为一个联合网络表达:

SELECT c.colorname, c.hexa, r.rgbvalue, g.rgbvalue, b.rgbvalue
FROM (SELECT colorname, hexa
      FROM sometable
      GROUP BY colorname) c
JOIN sometable r ON c.colorname = r.colorname AND r.rgb =  r 
JOIN sometable g ON c.colorname = g.colorname AND g.rgb =  g 
JOIN sometable b ON c.colorname = b.colorname AND b.rgb =  b 
;

Answer 2

执行

CREATE EXTENSION tablefunc;

页: 1

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