Oracle sql query with complex constraint - sql

Question

Table named T1 with following values
Col1 Col2 Col3
Rs1 S S2
Rs2 SX S3
Rs3 S S2
From a csv, I need to insert some values into the table, having values Rs4, SX and S3 respectively to each column.
I need to apply a check with following constraints.
One S3 can belong to only one SX, but S3 and SX as pair can belong can belong to multiple columns1's values.
What will be the oracle query for this? And if the above condition is true then I need to run an insertion query which is prepared. How can it validated?
PS: we can't create another table.

Answer 1

Had to do a little discovery after I was informed that I totally missed the ORACLE tag. Knowing what you do not know is very important to me. This post should be sufficiently different.
THE BASIC PROBLEM WITH ORACLE'S CHECK
A check constraint can NOT be defined on a SQL View. The check constraint defined on a table must refer to only columns in that
table. It can not refer to columns in other tables.
A check constraint can NOT include a SQL Subquery.
A check constraint can be defined in either a SQL CREATE TABLE statement or a SQL ALTER TABLE statement.
REVISITING THE PROBLEM
We know that (Col2,Col3)| #(Col2,COl3) >= 1.
We know that {Col1}∩(Col2,Col3)
However, the #Cardinality of Col1? Can it be more than 1?
Clearly, the business requirements are not fully explained.
REVISITING THE SOLUTIONS
Adding Objects to the database.
While adding additional tables has been voted down, is it possible to add an ID column? Assuming Col1 is NOT unique to the subsets of (Col2,COl3), then you can add a true ID Column that fulfills the need for normalization while providing true indexing power in your query.
Col1 Col2 Col3 Col4
Rs1 S S2 1
Rs2 SX S3 2
Rs3 S S2 1
To be clear, Col4 would still be an ID since the values of Col2, Col3 are determined by Col4. (Col2,Col3) 1:1 Col4.
CHECKS
Multiple CHECK constraints, each with a simple condition enforcing a
single business rule, are preferable to a single CHECK constraint with
a complicated condition enforcing multiple business rules ORACLE - Constraint
A single column can have multiple CHECK constraints that reference the
column in its definition. There is no limit to the number of CHECK
constraints that you can define on a column. ORACLE - Data Integrity
If you can add a column...by the love of monkeys, please do...not only will it make your life much easier, but you can also make QUERYING the table very efficient. However, for the rest of this post, I will assume you cannot add columns:
RESTATING THE PROBLEM IN CONSTRAINTS
Col2 may not appear with a different Col3. Vice Versa.
(Col2,Col3) may have multiple Co1...what is the possible Cardinality of Col1? Can it be repetitive? I read no.
WRITING OUT THE THEORY ON CHECKS
IF Col1 truly is unique in {(col2,col3)}, then the following already works:
ALTER TABLE EXAMPLE3
ADD CONSTRAINT ch_example3_3way UNIQUE (C, D, X) --only works if these valus never repeat.
The other main constraint #(Col2,Col3) > 1 simply cannot work unless you knew what value was being entered so as to enforce a real SARG. Any Col1 = Col1 or Col1 IN Col1 is the same thing as writing 1 = 1.
ON TRIGGERS
As tempting as the idea sounds, a quick glance through ORACLE lane left me warning against the use. Some reasons from ORACLE:
ORACLE - USING TRIGGERS
Do not create recursive triggers.
For example, if you create an AFTER UPDATE statement trigger on the
employees table, and the trigger itself issues an UPDATE statement on
the employees table, the trigger fires recursively until it runs out
of memory.
Use triggers on DATABASE judiciously. They are executed for every user every time the event occurs on which the trigger is created
Other problems include: TOADWORLD - ORACLE WIKI
Not Compiled -STORED PROCs can reuse a cached plan
No SELECT Trigger Support
Complete Trigger Failure
Disabled Triggers
No Version Control
Update OF COLUMN
No Support of SYS Table Triggers
Mutating Triggers
Hidden Behavior
Still, there are advantages of TRIGGERs, and you could still enforce data integrity by using a query where the first result of
SELECT Col2, Col3 FROM T1 WHERE ROWNUM = 1
Is compared to the inserted value *new.*Col2, *new.*Col3, but this would require the trigger to fire EVERY TIME a row was inserted...recompiled and everything,..I STRONGLY URGE AVOIDANCE.
STORED PROCS
Whatever you may think of STORED PROCEDURES, I suggest you consider them again. Everything from Functions, DML, DDL, database management, RECURSIVE LOGIC, sp_executesql, and beyond can be accomplished through a PROC.
Easily managed, provides encapsulation from accidental or malicious disabling or mutilization of coding.
PROCs are compiled once and can be reuse query plan caches, providing improved performances.
Provides superior portability, can be embedded into TRIGGERS, ORM framework, applications and beyond.
Can literally automate almost any function in a database including ETL, Resource management, security, and discovery. Views are commonly run through stored Procs.
THE UNIQUE ADVANTAGE OF ORACLE
Perhaps forgotten, consider that this is ORACLE which allows you to suspend CONSTRAINTS by inserting in the CONSTRAINT DEFFERABLE. From an ETL specialist perspective, this is essentially making a staging table out of your only table...which is pretty sweet in your predicament of having limited DDL rights.
CONCLUDING COMMENTS
There are a few efficient methods to delete duplicates in your data.
DELETE FROM T1
WHERE rowid NOT IN
(SELECT MAX(rowid)
FROM T1
GROUP BY Col1, Col2, Col3);
NOTE: rowid is the physical location of the row, while rownum represents the logical position in the query.
Lastly, my last attempt at rowid. Unfortunately, time is running late, and the free COMPILER from ORACLE is unhelpful. But I think the idea is what is important.
CREATE TABLE Example3 (MUT VARCHAR(50), D VARCHAR(50), X VARCHAR(50) );
INSERT INTO Example3 (MUT, D, X) VALUES('MUT', 'T', 'M' );
INSERT INTO Example3 (MUT, D, X) VALUES('MUT', 'T', 'P' );
INSERT INTO Example3 (MUT, D, X) VALUES('MUT', 'X', 'LP');
INSERT INTO Example3 (MUT, D, X) VALUES('MUT', 'X', 'Z');
INSERT INTO Example3 (MUT, D, X) VALUES('MUT', 'Y', 'POP');
SELECT C.D, B.X, B.rowid
FROM EXAMPLE3 A
LEFT OUTER JOIN (
SELECT DISTINCT X, C.rowid
FROM EXAMPLE3) B ON B.rowid = A.rowid
LEFT OUTER JOIN (
SELECT DISTINCT D, MAX(rowid) AS [rowid]
FROM Example3) C ON C.rowid = B.rowid

Answer 2

Finally, I'm able to resolve the question with a some select queries and few if conditions being applied. I have done this in a stored procedure.
SELECT count(col3)
INTO V_exist_value
FROM T3
WHERE col3's value = Variable_col3
AND col1's value <> Variable_col1
AND col2's value = Variable_col2;
IF (V_exist_value >= 1) THEN
INSERT INTO T3 (col1, col2, col3)
VALUES (Variable_col1, Variable_col2, Variable_col3);
ELSE
SELECT count(col3)
INTO V_exist_value1
FROM T3
WHERE col3's value = Variable_col3;
IF (V_exist_value1 = 0) THEN
INSERT INTO T3 (col1, col2, col3)
VALUES (Variable_col1, Variable_col2, Variable_col3);
ELSE
RAISE Exception_col3_value_exists;
END IF;
END IF;

Answer 3

If you don't want to use a trigger then you must normalize your tables.
Create a second table - say T1_PAIRS - that will store all permitted pairs of (col2, col3).
Create an unique constraint on col2 column in table T1_PAIRS - this constraint allows only for unique values of COL2 - for example no more than one S3 value can be used in all pairs ==> this enforces the rule: "One S3 can belong to only one SX"
Create a primary key on ( col2, col3 ) columns in this table T1_PAIRS.
Create a foreign key constraint on ( col2, col3 ) in T1 table that references the primary key of T1_PAIRS table.
In the end create an unique constraint on (col1, col2, col3) columnt to enforce a rule ==> S3 and SX as pair can belong can belong to multiple columns1's values (but no more than one value of column1)"
An example:
CREATE TABLE T1_PAIRS (
Col2 varchar2(10), Col3 varchar2(10),
CONSTRAINT T1_PAIRS_PK PRIMARY KEY( col2, col3 ),
CONSTRAINT T1_col2_UQ UNIQUE( col2 )
);
INSERT ALL
INTO T1_PAIRS( col2, col3 ) VALUES( 'S', 'S2' )
INTO T1_PAIRS( col2, col3 ) VALUES( 'SX', 'S3' )
SELECT 1 FROM dual;
ALTER TABLE T1
ADD CONSTRAINT col2_col3_pair_fk
FOREIGN KEY ( col2, col3 ) REFERENCES T1_pairs( col2, col3 );
ALTER TABLE T1
ADD CONSTRAINT pair_can_belong_to_multi_col1 UNIQUE( col1, col2, col3 );