Oracle 将行转为列

问题描述

我有以下表格:

TABLE1
------
id name
1  n1
2  n2


TABLE2
------
id tipo valor
1  t1   v1
1  t2   v2
2  t1   v1
2  t2   v5
2  t3   v3

我正在努力:

id name t1 t2 t3
1  n1   v1 v2 -
2  n2   v1 v5 v3

有可能吗?我一直在寻找示例，但仍然没有弄清楚.

Is it possible? I have been looking examples but still I don't get nothing clear.

谢谢！

推荐答案

一种选择是使用 PIVOT Clause

One option would be using PIVOT Clause

SELECT *
  FROM (SELECT t1.*, t2.tipo, t2.valor
          FROM table1 t1
          JOIN table2 t2
            ON t2.id = t1.id)
 PIVOT
 (
  MAX(valor) FOR tipo IN ( 't1' AS "t1", 't2' AS "t2", 't3' AS "t3" )
 )

但这是静态的，例如.需要更新 tipo 列的不同值.为了使其动态化，您可以创建一个函数

but this is static, eg. needs to be updated as different values for tipo column is added. In order to make it dynamic, you can create a function

CREATE OR REPLACE FUNCTION Get_Pivoted_Cols RETURN SYS_REFCURSOR IS
  v_recordset SYS_REFCURSOR;
  v_sql       VARCHAR2(32767);
  v_cols      VARCHAR2(32767);
BEGIN
  SELECT LISTAGG( ''''||tipo||''' AS "'||tipo||'"' , ',' )
          WITHIN GROUP ( ORDER BY tipo )
    INTO v_cols
    FROM ( SELECT DISTINCT tipo FROM table2 );

  v_sql := 'SELECT *
              FROM (SELECT t1.*, t2.tipo, t2.valor
                      FROM table1 t1
                      JOIN table2 t2
                        ON t2.id = t1.id)
             PIVOT
             (
              MAX(valor) FOR tipo IN ( '|| v_cols ||' )
             )';

  OPEN v_recordset FOR v_sql;
  RETURN v_recordset;
END;
/

然后使用调用

VAR rc REFCURSOR
EXEC :rc := Get_Pivoted_Cols;
PRINT rc

来自 SQL 开发人员的控制台.

from SQL developer's console.

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