Oracle 自然连接和计数(1)
有谁知道为什么在 Oracle 11g 中，当您使用多个自然连接执行 Count(1) 时，它会执行笛卡尔连接并导致计数偏离？
如
SELECT Count(1) FROM record NATURAL join address NATURAL join person WHERE status=1
AND code = 1 AND state = 'TN'
拉回300万行
SELECT * FROM record NATURAL join address NATURAL join person WHERE status=1
AND code = 1 AND state = 'TN'
This在拉回36000行时
，这是正确的数量。 我只是错过了什么吗？
这是我用来获得此结果的表格。
CREATE TABLE addresses (
address_id NUMBER(10,0) NOT NULL,
address_1 VARCHAR2(60) NULL,
address_2 VARCHAR2(60) NULL,
city VARCHAR2(35) NULL,
state CHAR(2) NULL,
zip VARCHAR2(5) NULL,
zip_4 VARCHAR2(4) NULL,
county VARCHAR2(35) NULL,
phone VARCHAR2(11) NULL,
fax VARCHAR2(11) NULL,
origin_network NUMBER(3,0) NOT NULL,
owner_network NUMBER(3,0) NOT NULL,
corrected_address_id NUMBER(10,0) NULL,
"HASH" VARCHAR2(200) NULL
);
CREATE TABLE rates (
rate_id NUMBER(10,0) NOT NULL,
eob VARCHAR2(30) NOT NULL,
network_code NUMBER(3,0) NOT NULL,
product_code VARCHAR2(2) NOT NULL,
rate_type NUMBER(1,0) NOT NULL
);
CREATE TABLE records (
pk_unique_id NUMBER(10,0) NOT NULL,
rate_id NUMBER(10,0) NOT NULL,
address_id NUMBER(10,0) NOT NULL,
effective_date DATE NOT NULL,
term_date DATE NULL,
last_update DATE NULL,
status CHAR(1) NOT NULL,
network_unique_id VARCHAR2(20) NULL,
rate_id_2 NUMBER(10,0) NULL,
contracted_by VARCHAR2(50) NULL,
contract_version VARCHAR2(5) NULL,
bill_address_id NUMBER(10,0) NULL
);
我应该提到这在 Oracle 9i 中不是问题，但是当我们切换到 11g 时它就成了问题。
Does anyone know why in Oracle 11g when you do a Count(1) with more than one natural join it does a cartesian join and throws the count way off?
Such as
SELECT Count(1) FROM record NATURAL join address NATURAL join person WHERE status=1
AND code = 1 AND state = 'TN'
This pulls back like 3 million rows when
SELECT * FROM record NATURAL join address NATURAL join person WHERE status=1
AND code = 1 AND state = 'TN'
pulls back like 36000 rows, which is the correct amount.
Am I just missing something?
Here are the tables I'm using to get this result.
CREATE TABLE addresses (
address_id NUMBER(10,0) NOT NULL,
address_1 VARCHAR2(60) NULL,
address_2 VARCHAR2(60) NULL,
city VARCHAR2(35) NULL,
state CHAR(2) NULL,
zip VARCHAR2(5) NULL,
zip_4 VARCHAR2(4) NULL,
county VARCHAR2(35) NULL,
phone VARCHAR2(11) NULL,
fax VARCHAR2(11) NULL,
origin_network NUMBER(3,0) NOT NULL,
owner_network NUMBER(3,0) NOT NULL,
corrected_address_id NUMBER(10,0) NULL,
"HASH" VARCHAR2(200) NULL
);
CREATE TABLE rates (
rate_id NUMBER(10,0) NOT NULL,
eob VARCHAR2(30) NOT NULL,
network_code NUMBER(3,0) NOT NULL,
product_code VARCHAR2(2) NOT NULL,
rate_type NUMBER(1,0) NOT NULL
);
CREATE TABLE records (
pk_unique_id NUMBER(10,0) NOT NULL,
rate_id NUMBER(10,0) NOT NULL,
address_id NUMBER(10,0) NOT NULL,
effective_date DATE NOT NULL,
term_date DATE NULL,
last_update DATE NULL,
status CHAR(1) NOT NULL,
network_unique_id VARCHAR2(20) NULL,
rate_id_2 NUMBER(10,0) NULL,
contracted_by VARCHAR2(50) NULL,
contract_version VARCHAR2(5) NULL,
bill_address_id NUMBER(10,0) NULL
);
I should mention this wasn't a problem in Oracle 9i, but when we switched to 11g it became a problem.
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评论（4）
我的建议是不要使用自然连接。 明确定义您的连接条件以避免混淆和“隐藏的错误”。 这是官方NATURAL JOIN Oracle文档和关于此的更多讨论主题。
My advice would be to NOT use NATURAL JOIN. Explicitly define your join conditions to avoid confusion and "hidden bugs". Here is the official NATURAL JOIN Oracle documentation and more discussion about this subject.
如果它完全按照您所说的那样发生，那么它一定是优化器错误，您应该将其报告给 Oracle。
If it happens exactly as you say then it must be an optimiser bug, you should report it to Oracle.
你应该尝试 count(*)
两者之间是有区别的。
count(1) 表示 1 不为空的行数
count(*) 表示计算行数
you should try a count(*)
There is a difference between the two.
count(1) signifies count rows where 1 is not null
count(*) signifies count the rows
刚刚注意到你使用了 2 个自然连接......
根据文档，您只能在 2 个表上使用自然连接
Natural_Join
Just noticed you used 2 natural joins...
From the documentation you can only use a natural join on 2 tables
Natural_Join