Oracle 将行转换为列

Question

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

我正在尝试获取：

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

可能吗？我一直在寻找示例，但仍然没有弄清楚。

谢谢！

Answer 1

您可以使用条件聚合：

select t1.id, t1.name,
    max(case when t2.typo = 't1' then t2.valor end) as t1,
    max(case when t2.typo = 't2' then t2.valor end) as t2,
    max(case when t2.typo = 't3' then t2.valor end) as t3
from table1 t1
inner join table2 t2 on t2.id = t1.id
group by t1.id, t1.name

typo 的 returns null 值不存在。如果你想要 '-'，你可以用 coalesce() 包围条件聚合，像这样：

    coalesce(max(case when t2.typo = 't1' then t2.valor end), '-') as t1

Answer 2

一个选项是使用 PIVOT 子句

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，因为添加了 tipo 列的不同值。为了让它动态化，你可以创建一个函数

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 开发者控制台。

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Oracle 将行转换为列

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