If a then b check in where clause - sql

Question

I am performing some data quality checks to identify bad data, I am unable to figure out how I can perform a check-such that the data is accurately mapped based on Value 1 vs Value 2.
I ultimately need to identify all IDs in T1 that have incorrect mapping in T2.I have used the following code but doesn't seem to give desired result. The mapping is not in the database and is a rule based on which the data needs to be entered.
- When value in: Apples,Bananas,Cherries,Pears,Kiwis - then it should be mapped to Fruit
- when value in: Cheese - then Cheese
- when value in: Cashews,Almonds - then Nuts
- when value in: Skittles - then Candy
- when value in: Chocolate - then null
Edit: I have added the desired output.
SELECT t1.id, t2.*
FROM t1,t2,t3
WHERE
t1.id = t2.id
AND (
(t2.value1_id IN (01,04,05,08,09) AND t2.value2_id <> 2)
OR (t2.value1_id = 02 and t2.value2_id <> 3)
OR (t2.value1_id IN (03,10) and t2.value2_id <> 1)
OR (t2.value1_id = 06 AND t2.value2_id <> 4)
OR (t2.value1_id = 07 AND t2.value_id IS NOT NULL)
)
T1
ID
1
2
3
4
5
6
7
T2
T1.ID Value1_ID Value2_ID
1 01 2
1 02 3
1 03 1
2 04 2
2 05 2
2 02 3
2 06 4
2 07
3 08 2
3 02 3
4 09 2
4 10 1
5 02 2
5 10 1
6 04 3
6 10 2
7 07 2
T3
ID Value1
01 Apples
02 Cheese
03 Cashews
04 Bananas
05 Cherries
06 Skittles
07 Chocolate
08 Pears
09 Kiwis
10 Almonds
T4
ID Value2
1 Nuts
2 Fruit
3 Cheese
4 Candy
Desired Output:
T1.ID Value1_ID Value2_ID
5 02 2
6 04 3
6 10 2
7 07 2
T1.ID 5, value1_id 02 is in the desired output as Cheese is mapped to Fruit
T1.ID 6, value1_id 04 - Bananas is mapped to Cheese
T1.ID 6, value1_id 10 - Almonds is mapped to Fruit
T1.ID 7, value1_id 07 - Chocolate is mapped to Fruit when it should be null

Answer 1

One of the problems is that - when looking at T2 - it is not easy to tell whether a "mapping" is correct or not.
When creating the test data for T1 and T2, we have used CHARs for VALUE1_IDs, in order to make the subsequent queries a bit more "readable".
Tables
create table T1( id primary key )
as
select 1 from dual union all
select 2 from dual union all
select 3 from dual ;
create table T2 ( id, value1_id, value2_id )
as
select 1, '01', 2 from dual union all
select 1, '02', 3 from dual union all
select 1, '03', 1 from dual union all
select 2, '04', 2 from dual union all
select 2, '05', 2 from dual union all
select 2, '02', 3 from dual union all
select 2, '06', 4 from dual union all
select 2, '07', null from dual union all
select 3, '08', 2 from dual union all
select 3, '02', 3 from dual union all
select 4, '09', 2 from dual union all
select 4, '10', 1 from dual ;
Refactored query
--
-- find incorrect mappings
--
select t2.*, 'T1 id not valid' as status
from t2
where t2.id not in ( select id from T1 )
union all
select t2.*, 'value1_id <-> value2_id mapping incorrect '
from t1 join t2 on t1.id = t2.id
where
( t2.value1_id in ('01','04','05','08','09') and t2.value2_id <> 2 )
or
( t2.value1_id = '02' and t2.value2_id <> 3 )
or
( t2.value1_id in ('03','10') and t2.value2_id <> 1 )
or
( t2.value1_id = '06' and t2.value2_id <> 4 )
or
( t2.value1_id = '07' and t2.value2_id is null )
;
-- result
ID VALUE1_ID VALUE2_ID STATUS
4 10 1 T1 id not valid
4 09 2 T1 id not valid
2 07 NULL value1_id <-> value2_id mapping incorrect
DBfiddle
ALTERNATIVE
Another possibility may be: create a table, containing all valid mappings, in "human readable" form, and use it to validate the mappings stored in T2. However, use whatever approach you are more comfortable with - as long as you get the correct results. Example (tested w/ Oracle 12c, 18c)
-- in addition to tables T1, T2, T3, and T4: table with correct mappings
create table map( category, product )
as
select 'Fruit', 'Apples' from dual union all
select 'Cheese', 'Cheese' from dual union all
select 'Nuts', 'Cashews' from dual union all
select 'Fruit', 'Bananas' from dual union all
select 'Fruit', 'Cherries' from dual union all
select 'Candy', 'Skittles' from dual union all
select 'Candy', 'Chocolate' from dual union all
select 'Fruit', 'Pears' from dual union all
select 'Fruit', 'Kiwis' from dual union all
select 'Nuts', 'Almonds' from dual;
-- make sure that the entries in the MAP table tie in with T3 and T4
alter table map
add (
constraint m_pk primary key ( category, product )
, constraint m_category_fk foreign key ( category ) references T4 ( value2 )
, constraint m_product_fk foreign key ( product ) references T3 ( value1 )
) ;
Find incorrect mappings
-- T2 rows containing incorrect (invalid) mappings
-- -> all rows MINUS the correct ones
select T2.id, T2.value1_id, T2.value2_id
from T2
minus (
select T2.id, T2.value1_id, T2.value2_id
from T2
join (
--
select T4.id categoryid, T3.id productid, M.category, M.product
from T4
join map M on T4.value2 = M.category
join T3 on T3.value1 = M.product
--
) C -- correct mappings
on
C.productid = T2.value1_id
and C.categoryid = T2.value2_id
) ;
-- result
ID VALUE1_ID VALUE2_ID
2 07 NULL
DBfiddle

Answer 2

I would highly recommend that you create a table to represent the one-to-many relationship between T4 and T3. This would represent a first step towards fixing your design, while providing a simple way to solve your current question.
Here is a CREATE TABLE ... AS SELECT order that initializes such a table with your sample data :
create table cat AS
SELECT 1 t3_id, 2 t4_id FROM DUAL
UNION ALL SELECT 4, 2 FROM DUAL
UNION ALL SELECT 5, 2 FROM DUAL
UNION ALL SELECT 8, 2 FROM DUAL
UNION ALL SELECT 9, 2 FROM DUAL
UNION ALL SELECT 2, 3 FROM DUAL
UNION ALL SELECT 3, 1 FROM DUAL
UNION ALL SELECT 10, 1 FROM DUAL
UNION ALL SELECT 6, 4 FROM DUAL
UNION ALL SELECT 7, NULL FROM DUAL
;
With this table in place, indentifiying records incorrectly mapped is as simple as :
SELECT t2.*
FROM t2
WHERE t2.Value2_ID IS NOT NULL AND NOT EXISTS (
SELECT 1 FROM cat WHERE cat.t3_id = t2.Value1_ID AND cat.t4_id = t2.Value2_ID
)
This DB Fiddle demo with your sample data yields :
T1_ID | VALUE1_ID | VALUE2_ID
----: | --------: | --------:
5 | 2 | 2
6 | 4 | 3
6 | 10 | 2
7 | 7 | 2
Hint to further improve your design : you have a one-to-many relationship between T4 (families of aliments) and T3 (aliments). The classic way to represent this is to add a column in the child table (T3) that references the parent table.

Answer 3

If you can't create a table with the mappings from fruit to categories and you know that the values are static then just include the mappings into your query using a nested sub-query or a sub-query factoring clause:
Oracle Setup:
create table T2 ( id, value1_id, value2_id ) as
select 1, '01', 2 from dual union all
select 1, '02', 3 from dual union all
select 1, '03', 1 from dual union all
select 2, '04', 2 from dual union all
select 2, '05', 2 from dual union all
select 2, '02', 3 from dual union all
select 2, '06', 4 from dual union all
select 2, '07', null from dual union all
select 3, '08', 2 from dual union all
select 3, '02', 3 from dual union all
select 4, '09', 2 from dual union all
select 4, '10', 1 from dual union all
select 5, '02', 2 from dual union all
select 5, '10', 1 from dual union all
select 6, '04', 3 from dual union all
select 6, '10', 2 from dual union all
select 7, '07', 2 from dual;
Query:
WITH mappings ( name, category ) AS (
SELECT '01', 2 FROM DUAL UNION ALL
SELECT '02', 3 FROM DUAL UNION ALL
SELECT '03', 1 FROM DUAL UNION ALL
SELECT '04', 2 FROM DUAL UNION ALL
SELECT '05', 2 FROM DUAL UNION ALL
SELECT '06', 4 FROM DUAL UNION ALL
SELECT '07', NULL FROM DUAL UNION ALL
SELECT '08', 2 FROM DUAL UNION ALL
SELECT '09', 2 FROM DUAL UNION ALL
SELECT '10', 1 FROM DUAL
)
SELECT *
FROM T2 t
WHERE NOT EXISTS (
SELECT 1
FROM mappings m
WHERE t.value1_id = m.name
AND ( t.value2_id = m.category
OR ( t.value2_id IS NULL AND m.category IS NULL ) )
);
Results:
ID | VALUE1_ID | VALUE2_ID
-: | :-------- | --------:
5 | 02 | 2
6 | 04 | 3
6 | 10 | 2
7 | 07 | 2
db<>fiddle here