从 SQL 表在 SQL 中创建数据透视视图

A stored function(or procedure) might be created in order to create a SQL for Dynamic Pivoting, and the result set is loaded into a variable of type SYS_REFCURSOR :

CREATE OR REPLACE FUNCTION Get_Categories_RS RETURN SYS_REFCURSOR IS
  v_recordset SYS_REFCURSOR;
  v_sql       VARCHAR2(32767);
  v_cols_1    VARCHAR2(32767);
  v_cols_2    VARCHAR2(32767);  
BEGIN
  SELECT LISTAGG( ''''||"level"||''' AS "'||"level"||'"' , ',' )
          WITHIN GROUP ( ORDER BY "level" DESC )
    INTO v_cols_1
    FROM (
          SELECT DISTINCT "level"
            FROM temp
          );

  SELECT LISTAGG( 'MAX(CASE WHEN category = '''||category||''' THEN "'||"level"||'" END) AS "'||"level"||'_'||category||'"' , ',' )
          WITHIN GROUP ( ORDER BY category, "level" DESC )
    INTO v_cols_2
    FROM (
          SELECT DISTINCT "level", category
            FROM temp
          );

  v_sql :=
  'SELECT "set", '|| v_cols_2 ||'
     FROM
     (
      SELECT *
        FROM temp
       PIVOT
       (
        MAX(value) FOR "level" IN ( '|| v_cols_1 ||' )
       )
      )
      GROUP BY "set"
      ORDER BY "set"'; 

  OPEN v_recordset FOR v_sql;
  RETURN v_recordset;
END;

其中我使用了两个级别的透视:第一个是在涉及 PIVOT 子句的内部查询中，第二个是在具有条件聚合逻辑的外部查询中.请注意，在符合描述的预期结果中，级别的顺序应按降序排列(Z、Y、X).

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