我知道PHP和MYSQL在某种程度上回答了这个问题,但我想知道是否有人可以教我在Oracle 10g (最好是)和11g中将字符串(逗号分隔)拆分为多行的最简单方法。
如下表所示:
Name | Project | Error
108 test Err1, Err2, Err3
109 test2 Err1
我想创建以下内容:
Name | Project | Error
108 Test Err1
108 Test Err2
108 Test Err3
109 Test2 Err1
我已经看到了一些关于堆栈的潜在解决方案,但它们只占单个列(逗号分隔的字符串)。任何帮助都将不胜感激。
发布于 2013-01-15 12:12:10
正则表达式是一件很棒的事情:)
with temp as (
select 108 Name, 'test' Project, 'Err1, Err2, Err3' Error from dual
union all
select 109, 'test2', 'Err1' from dual
)
SELECT distinct Name, Project, trim(regexp_substr(str, '[^,]+', 1, level)) str
FROM (SELECT Name, Project, Error str FROM temp) t
CONNECT BY instr(str, ',', 1, level - 1) > 0
order by Name
发布于 2013-01-18 04:27:59
下面是几个相同的例子:
SELECT trim(regexp_substr('Err1, Err2, Err3', '[^,]+', 1, LEVEL)) str_2_tab
FROM dual
CONNECT BY LEVEL <= regexp_count('Err1, Err2, Err3', ',')+1
/
SELECT trim(regexp_substr('Err1, Err2, Err3', '[^,]+', 1, LEVEL)) str_2_tab
FROM dual
CONNECT BY LEVEL <= length('Err1, Err2, Err3') - length(REPLACE('Err1, Err2, Err3', ',', ''))+1
/
此外,还可以使用DBMS_UTILITY.comma_to_table & table_to_comma:http://www.oracle-base.com/articles/9i/useful-procedures-and-functions-9i.php#DBMS_UTILITY.comma_to_table
发布于 2016-10-27 21:55:40
我想提出一种使用流水线化表函数的不同方法。它有点类似于XMLTABLE的技术,只是您提供了自己的自定义函数来拆分字符串:
-- Create a collection type to hold the results
CREATE OR REPLACE TYPE typ_str2tbl_nst AS TABLE OF VARCHAR2(30);
/
-- Split the string according to the specified delimiter
CREATE OR REPLACE FUNCTION str2tbl (
p_string VARCHAR2,
p_delimiter CHAR DEFAULT ','
)
RETURN typ_str2tbl_nst PIPELINED
AS
l_tmp VARCHAR2(32000) := p_string || p_delimiter;
l_pos NUMBER;
BEGIN
LOOP
l_pos := INSTR( l_tmp, p_delimiter );
EXIT WHEN NVL( l_pos, 0 ) = 0;
PIPE ROW ( RTRIM( LTRIM( SUBSTR( l_tmp, 1, l_pos-1) ) ) );
l_tmp := SUBSTR( l_tmp, l_pos+1 );
END LOOP;
END str2tbl;
/
-- The problem solution
SELECT name,
project,
TRIM(COLUMN_VALUE) error
FROM t, TABLE(str2tbl(error));
结果:
NAME PROJECT ERROR
---------- ---------- --------------------
108 test Err1
108 test Err2
108 test Err3
109 test2 Err1
这种方法的问题在于,优化器通常不知道表函数的基数,因此必须进行猜测。这可能会对您的执行计划造成潜在的危害,因此可以扩展此解决方案,为优化器提供执行统计信息。
您可以通过在上面的查询上运行一个EXPLAIN计划来查看这个优化器估计:
Execution Plan
----------------------------------------------------------
Plan hash value: 2402555806
----------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 16336 | 366K| 59 (0)| 00:00:01 |
| 1 | NESTED LOOPS | | 16336 | 366K| 59 (0)| 00:00:01 |
| 2 | TABLE ACCESS FULL | T | 2 | 42 | 3 (0)| 00:00:01 |
| 3 | COLLECTION ITERATOR PICKLER FETCH| STR2TBL | 8168 | 16336 | 28 (0)| 00:00:01 |
----------------------------------------------------------------------------------------------
即使该集合只有3个值,优化器也为它估计了8168行(默认值)。乍一看,这似乎无关紧要,但这可能足以让优化器决定一个次优计划。
解决方案是使用优化器扩展为集合提供统计信息:
-- Create the optimizer interface to the str2tbl function
CREATE OR REPLACE TYPE typ_str2tbl_stats AS OBJECT (
dummy NUMBER,
STATIC FUNCTION ODCIGetInterfaces ( p_interfaces OUT SYS.ODCIObjectList )
RETURN NUMBER,
STATIC FUNCTION ODCIStatsTableFunction ( p_function IN SYS.ODCIFuncInfo,
p_stats OUT SYS.ODCITabFuncStats,
p_args IN SYS.ODCIArgDescList,
p_string IN VARCHAR2,
p_delimiter IN CHAR DEFAULT ',' )
RETURN NUMBER
);
/
-- Optimizer interface implementation
CREATE OR REPLACE TYPE BODY typ_str2tbl_stats
AS
STATIC FUNCTION ODCIGetInterfaces ( p_interfaces OUT SYS.ODCIObjectList )
RETURN NUMBER
AS
BEGIN
p_interfaces := SYS.ODCIObjectList ( SYS.ODCIObject ('SYS', 'ODCISTATS2') );
RETURN ODCIConst.SUCCESS;
END ODCIGetInterfaces;
-- This function is responsible for returning the cardinality estimate
STATIC FUNCTION ODCIStatsTableFunction ( p_function IN SYS.ODCIFuncInfo,
p_stats OUT SYS.ODCITabFuncStats,
p_args IN SYS.ODCIArgDescList,
p_string IN VARCHAR2,
p_delimiter IN CHAR DEFAULT ',' )
RETURN NUMBER
AS
BEGIN
-- I'm using basically half the string lenght as an estimator for its cardinality
p_stats := SYS.ODCITabFuncStats( CEIL( LENGTH( p_string ) / 2 ) );
RETURN ODCIConst.SUCCESS;
END ODCIStatsTableFunction;
END;
/
-- Associate our optimizer extension with the PIPELINED function
ASSOCIATE STATISTICS WITH FUNCTIONS str2tbl USING typ_str2tbl_stats;
测试生成的执行计划:
Execution Plan
----------------------------------------------------------
Plan hash value: 2402555806
----------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 23 | 59 (0)| 00:00:01 |
| 1 | NESTED LOOPS | | 1 | 23 | 59 (0)| 00:00:01 |
| 2 | TABLE ACCESS FULL | T | 2 | 42 | 3 (0)| 00:00:01 |
| 3 | COLLECTION ITERATOR PICKLER FETCH| STR2TBL | 1 | 2 | 28 (0)| 00:00:01 |
----------------------------------------------------------------------------------------------
正如您所看到的,上面计划中的基数不再是8196的猜测值。这仍然是不正确的,因为我们将一个列而不是字符串文字传递给函数。
在这种特殊情况下,有必要对函数代码进行一些调整,以给出更接近的估计,但我认为总体概念在这里已经解释得很清楚了。
本答案中使用的str2tbl函数最初是由Tom Kyte开发的:https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:110612348061
通过阅读本文,可以进一步探索将统计数据与对象类型相关联的概念:http://www.oracle-developer.net/display.php?id=427
这里描述的技术在10g+中有效。
https://stackoverflow.com/questions/14328621
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