换位表我有一个表,如:通过选择查询
Key type value
---------------------
40 A 12.34
41 A 10.24
41 B 12.89
我想它的格式为:
Types 40 41 42 (keys)
---------------------------------
A 12.34 10.24 XXX
B YYY 12.89 ZZZ
这怎么可能通过SQL查询来完成。案例陈述,解码?
换位表我有一个表,如:通过选择查询
Key type value
---------------------
40 A 12.34
41 A 10.24
41 B 12.89
我想它的格式为:
Types 40 41 42 (keys)
---------------------------------
A 12.34 10.24 XXX
B YYY 12.89 ZZZ
这怎么可能通过SQL查询来完成。案例陈述,解码?
你正在寻找所谓的“pivot”(也称“Pivoting Operations”看到Oracle数据库数据仓库指南):
SELECT *
FROM tbl
PIVOT(SUM(value) FOR Key IN (40, 41, 42))
它加入到Oracle 11g中。请注意,您需要在pivot子句中指定结果列(来自未转义列的值,它们将成为pivoted列名称)。任何未在数据透视表中指定的列都被隐式分组。如果原始表中的列不想分组,请从视图或子查询中选择,而不是从表中选择。
您可以参与一点wizardry并让Oracle为您创建语句,以便您无需弄清楚需要在哪些列上进行转换。在11g中,当你知道列值的数字:
SELECT
'SELECT * FROM tbl PIVOT(SUM(value) FOR Key IN ('
|| LISTAGG(Key, ',') WITHIN GROUP (ORDER BY Key)
|| ');'
FROM tbl;
如果列的值可能不是数字:
SELECT
'SELECT * FROM tbl PIVOT(SUM(value) FOR Key IN (\''
|| LISTAGG(Key, '\',\'') WITHIN GROUP (ORDER BY Key)
|| '\'));'
FROM tbl;
LISTAGG
可能重复重复(?有人要测试这个),在这种情况下,你需要:
SELECT
'SELECT * FROM tbl PIVOT(SUM(value) FOR Key IN (\''
|| LISTAGG(Key, '\',\'') WITHIN GROUP (ORDER BY Key)
|| '\'));'
FROM (SELECT DISTINCT Key FROM tbl);
你可以走的更远,定义一个函数,它接受一个表名,合计表达和枢轴列名,通过第一p返回一个支点声明然后再评估上述说法。然后,您可以定义一个采用相同参数并生成旋转结果的过程。我没有访问到Oracle 11g测试它,但我相信它会看起来像:
CREATE PACKAGE dynamic_pivot AS
-- creates a PIVOT statement dynamically
FUNCTION pivot_stmt (tbl_name IN varchar2(30),
pivot_col IN varchar2(30),
aggr IN varchar2(40),
quote_values IN BOOLEAN DEFAULT TRUE)
RETURN varchar2(300);
PRAGMA RESTRICT_REFERENCES (pivot_stmt, WNDS, RNPS);
-- creates & executes a PIVOT
PROCEDURE pivot_table (tbl_name IN varchar2(30),
pivot_col IN varchar2(30),
aggr IN varchar2(40),
quote_values IN BOOLEAN DEFAULT TRUE);
END dynamic_pivot;
CREATE PACKAGE BODY dynamic_pivot AS
FUNCTION pivot_stmt (
tbl_name IN varchar2(30),
pivot_col IN varchar2(30),
aggr_expr IN varchar2(40),
quote_values IN BOOLEAN DEFAULT TRUE
) RETURN varchar2(300)
IS
stmt VARCHAR2(400);
quote VARCHAR2(2) DEFAULT '';
BEGIN
IF quote_values THEN
quote := '\\\'';
END IF;
-- "\||" shows that you are still in the dynamic statement string
-- The input fields aren't sanitized, so this is vulnerable to injection
EXECUTE IMMEDIATE 'SELECT \'SELECT * FROM ' || tbl_name
|| ' PIVOT(' || aggr_expr || ' FOR ' || pivot_col
|| ' IN (' || quote || '\' \|| LISTAGG(' || pivot_col
|| ', \'' || quote || ',' || quote
|| '\') WITHIN GROUP (ORDER BY ' || pivot_col || ') \|| \'' || quote
|| '));\' FROM (SELECT DISTINCT ' || pivot_col || ' FROM ' || tbl_name || ');'
INTO stmt;
RETURN stmt;
END pivot_stmt;
PROCEDURE pivot_table (tbl_name IN varchar2(30), pivot_col IN varchar2(30), aggr_expr IN varchar2(40), quote_values IN BOOLEAN DEFAULT TRUE) IS
BEGIN
EXECUTE IMMEDIATE pivot_stmt(tbl_name, pivot_col, aggr_expr, quote_values);
END pivot_table;
END dynamic_pivot;
注:tbl_name
,pivot_col
和aggr_expr
参数的长度来自maximum table and column name length。还要注意该函数容易受到SQL注入的影响。
在pre-11g中,您可以应用MySQL pivot statement generation技术(根据显式定义每个枢轴值的单独列来生成他人发布的查询类型)。
从来没有尝试过,但似乎至少甲骨文11具有枢条款
枢轴确实大大简化事情。但是,在11g之前,您需要手动执行此操作。
select
type,
sum(case when key = 40 then value end) as val_40,
sum(case when key = 41 then value end) as val_41,
sum(case when key = 42 then value end) as val_42
from my_table
group by type;
如果您无权访问11g,则可以使用字符串聚合和分组方法来约略。您正在寻找诸如
with data as(
SELECT 40 KEY , 'A' TYPE , 12.34 VALUE FROM DUAL UNION
SELECT 41 KEY , 'A' TYPE , 10.24 VALUE FROM DUAL UNION
SELECT 41 KEY , 'B' TYPE , 12.89 VALUE FROM DUAL
)
select
TYPE ,
wm_concat(KEY) KEY ,
wm_concat(VALUE) VALUE
from data
GROUP BY TYPE;
type KEY VALUE
------ ------- -----------
A 40,41 12.34,10.24
B 41 12.89
这是什么是根据wm_concat如下所示:http://www.oracle-base.com/articles/misc/StringAggregationTechniques.php
我要以防万一它有助于离开这里,但我觉得PIVOT或MikeyByCrikey的回答会在重新查看您的样本结果后,最符合您的需求。
它适用于Oracle 11,但对于早期版本,方法在此处提供http://www.orafaq.com/wiki/PIVOT – 2010-12-10 14:20:01