给定两个表格，它们之间没有任何关系。 你能确定两列处于未申报关系的概率吗？
只是为了让我理解：你可以采取任何相关的表格。您删除它们之间的引用。您能否仅通过使用过程语言或一系列SQL脚本检查其内容来猜测原始关系（假设您有足够的数据需要）？
与失踪关系相关还有另一个问题：Find Missing Relationships using PL/SQL。在这里，用户已经知道参与缺失关系的列。在我的情况下，我想检测哪些列。
您可以举例说明您使用的任何数据库类型（SqlServer，Oracle，MySql等...）
答案 0 :(得分：0)
我创造了这样的尝试。可以改进很多。
DO $$
DECLARE
value int := 0;
schema_name_1 text;
table_name_1 text;
column_name_1 text;
sql_1 text;
res_1 record;
schema_name_2 text;
table_name_2 text;
column_name_2 text;
sql_2 text;
res_2 record;
BEGIN
schema_name_1='public';
table_name_1='Table1';
column_name_1='"Id"';
schema_name_2='public';
table_name_2='Table2';
column_name_2='"Id"';
DROP TABLE IF EXISTS _x;
CREATE TEMPORARY TABLE _x (
"Info" text,
"C1" text,
"C2" text,
"Sql1" text,
"Sql2" text
);
sql_1 := concat('ALTER TABLE _x RENAME COLUMN "C1" TO "', schema_name_1, '.', table_name_1, '";');
sql_2 := concat('ALTER TABLE _x RENAME COLUMN "C2" TO "', schema_name_2, '.', table_name_2, '";');
EXECUTE sql_1;
EXECUTE sql_2;
BEGIN
-------------------------------------------------------------------------------------------------------------------------------
sql_1 := concat('SELECT count(t1.', column_name_1, ') AS count FROM ', schema_name_1, '."', table_name_1, '" AS t1;');
sql_2 := concat('SELECT count(t2.', column_name_2, ') AS count FROM ', schema_name_2, '."', table_name_2, '" AS t2;');
res_1 = null;
res_2 = null;
FOR res_1 IN EXECUTE sql_1 LOOP
INSERT INTO _x VALUES (
'Count',
res_1.count,
0,
sql_1,
sql_2
);
END LOOP;
FOR res_2 IN EXECUTE sql_2 LOOP
sql_2 := concat('UPDATE _x SET "', schema_name_2, '.', table_name_2, '" = ', res_2.count, ' WHERE "Info" = ''Count'';');
EXECUTE sql_2;
END LOOP;
RAISE NOTICE '%, %, %', res_1.count, res_2.count, sql_1;
-------------------------------------------------------------------------------------------------------------------------------
sql_1 = concat('SELECT count(DISTINCT(t1.', column_name_1, ')) AS count FROM ', schema_name_1, '."', table_name_1, '" AS t1;');
sql_2 = concat('SELECT count(DISTINCT(t2.', column_name_2, ')) AS count FROM ', schema_name_2, '."', table_name_2, '" AS t2;');
res_1 = null;
res_2 = null;
FOR res_1 IN EXECUTE sql_1 LOOP
INSERT INTO _x VALUES (
'Distinct Count',
res_1.count,
0,
sql_1,
sql_2
);
END LOOP;
FOR res_2 IN EXECUTE sql_2 LOOP
sql_2 := concat('UPDATE _x SET "', schema_name_2, '.', table_name_2, '" = ', res_2.count, ' WHERE "Info" = ''Distinct Count'';');
EXECUTE sql_2;
END LOOP;
RAISE NOTICE '%, %, %', res_1.count, res_2.count, sql_1;
-------------------------------------------------------------------------------------------------------------------------------
sql_1 = concat('SELECT count(t1.', column_name_1, ') AS count FROM ', schema_name_1, '."', table_name_1, '" AS t1 JOIN ', schema_name_2, '."', table_name_2, '" AS t2 ON t1.', column_name_1, '= t2.', column_name_2, ';');
sql_2 = concat('SELECT count(t2.', column_name_2, ') AS count FROM ', schema_name_2, '."', table_name_2, '" AS t2 JOIN ', schema_name_1, '."', table_name_1, '" AS t1 ON t1.', column_name_1, '= t2.', column_name_2, ';');
res_1 = null;
res_2 = null;
FOR res_1 IN EXECUTE sql_1 LOOP
INSERT INTO _x VALUES (
'Matched',
res_1.count,
0,
sql_1,
sql_2
);
END LOOP;
FOR res_2 IN EXECUTE sql_2 LOOP
sql_2 := concat('UPDATE _x SET "', schema_name_2, '.', table_name_2, '" = ', res_2.count, ' WHERE "Info" = ''Matched'';');
EXECUTE sql_2;
END LOOP;
RAISE NOTICE '%, %, %', res_1.count, res_2.count, sql_1;
-------------------------------------------------------------------------------------------------------------------------------
sql_1 = concat('SELECT count(t1.', column_name_1, ') AS count FROM ', schema_name_1, '."', table_name_1, '" AS t1 LEFT JOIN ', schema_name_2, '."', table_name_2, '" AS t2 ON t1.', column_name_1, '= t2.', column_name_2, ' WHERE t2.', column_name_2, ' IS NULL;');
sql_2 = concat('SELECT count(t2.', column_name_2, ') AS count FROM ', schema_name_2, '."', table_name_2, '" AS t2 LEFT JOIN ', schema_name_1, '."', table_name_1, '" AS t1 ON t1.', column_name_1, '= t2.', column_name_2, ' WHERE t1.', column_name_1, ' IS NULL;');
res_1 = null;
res_2 = null;
FOR res_1 IN EXECUTE sql_1 LOOP
INSERT INTO _x VALUES (
'Unlinked',
res_1.count,
0,
sql_1,
sql_2
);
END LOOP;
FOR res_2 IN EXECUTE sql_2 LOOP
sql_2 := concat('UPDATE _x SET "', schema_name_2, '.', table_name_2, '" = ', res_2.count, ' WHERE "Info" = ''Unlinked'';');
EXECUTE sql_2;
END LOOP;
RAISE NOTICE '%, %, %', res_1.count, res_2.count, sql_1;
-------------------------------------------------------------------------------------------------------------------------------
sql_1 = concat('SELECT MAX(t.count0) AS count FROM (SELECT count(*) AS count0 FROM ', schema_name_1, '."', table_name_1, '" AS t1 JOIN ', schema_name_2, '."', table_name_2, '" AS t2 ON t1.', column_name_1, '= t2.', column_name_2, ' GROUP BY t2.', column_name_2, ') AS t;');
sql_2 = concat('SELECT MAX(t.count0) AS count FROM (SELECT count(*) AS count0 FROM ', schema_name_2, '."', table_name_2, '" AS t2 JOIN ', schema_name_1, '."', table_name_1, '" AS t1 ON t1.', column_name_1, '= t2.', column_name_2, ' GROUP BY t1.', column_name_1, ') as t;');
res_1 = null;
res_2 = null;
FOR res_1 IN EXECUTE sql_1 LOOP
INSERT INTO _x VALUES (
'Multiplicity',
res_1.count,
0,
sql_1,
sql_2
);
END LOOP;
FOR res_2 IN EXECUTE sql_2 LOOP
sql_2 := concat('UPDATE _x SET "', schema_name_2, '.', table_name_2, '" = ', res_2.count, ' WHERE "Info" = ''Multiplicity'';');
EXECUTE sql_2;
END LOOP;
RAISE NOTICE '%, %, %', res_1.count, res_2.count, sql_1;
-------------------------------------------------------------------------------------------------------------------------------
END;
END; $$;
SELECT * FROM _x;
输出：
|------------------------------------------------------------------------------------------------------------------------|
|Info | Table1.Id | Table2.Id | SQL1 |
|-----------------+-----------+-----------+------------------------------------------------------------------------------|
|"Count" |"7386359" |"12264" | "SELECT count(t1."Id") AS count FROM public."Table1" AS t1 |
|-----------------------------------------+------------------------------------------------------------------------------|
|"Distinct Count" |"7386359" |"12264" | "SELECT count(DISTINCT(t1."Id")) AS count FROM public."Table1" AS t1 |
|-----------------+-----------+-----------+------------------------------------------------------------------------------|
|"Matched" |"12264" |"12264" | "SELECT count(t1."Id") AS count FROM public."Table1" AS t1 |
| | | | JOIN public."Table2" AS t2 ON t1."Id"= t2."Id" |
|-----------------+-----------+-----------+------------------------------------------------------------------------------|
|"Unlinked" |"7374095" |"0" | "SELECT count(t1."Id") AS count FROM public."Table1" AS t1 |
| | | | LEFT JOIN public."Table2" AS t2 ON t1."Id"= t2."Id" WHERE t2."Id" IS NULL|
|-----------------+-----------+-----------+------------------------------------------------------------------------------|
|"Multiplicity" |"1" |"1" | "SELECT MAX(t.count0) AS count FROM (SELECT count(*) AS count0 |
| | | | FROM public."Table1" AS t1 JOIN public."Table1" AS t2 ON t1."Id"= t2."Id"|
| | | | GROUP BY t2."Id") AS t |
|------------------------------------------------------------------------------------------------------------------------|