Delete a record based on multiple table choices SQL - sql

Question

I'm trying to wrap my head around how to accomplish this Delete query. The goal is I'm trying to delete a client record (main table) based on if they don't have an insurance policy (another table) and if their needs description is "transportation" and importance values is LESS than 5. The needs is another table. They are all connected with foreign keys and SSN as the connector and Delete cascade is working properly. The query is partially working as is. If there is no insurance policy, the Client is being deleted correctly. However, the need description and importance value factors are not currently working. It will still delete if I have no insurance policy, but my importance description is another value other than transportation.
It's almost like I need 2 subqueries compare both Needs table and Insurance_Policy table for deletion, but I don't know how to do that.
The database I'm using is Azure Data Studio
Here is my current Procedure code:
DROP PROCEDURE IF EXISTS Option17;
GO
CREATE PROCEDURE Option17
AS
BEGIN
DELETE FROM Client
WHERE Client.SSN NOT IN (SELECT I.SSN
FROM Insurance_Policy I, Needs N
WHERE Client.SSN = I.SSN
AND Client.SSN = N.SSN
AND N.need_description = 'transportation'
AND N.importance_value < 5)
END
Also, here are my table structures:
CREATE TABLE Client
(
SSN VARCHAR(9),
doctor_name VARCHAR(60),
doctor_phone_no VARCHAR(10),
lawyer_name VARCHAR(60),
lawyer_phone_no VARCHAR(10),
date_assigned DATE,
PRIMARY KEY (SSN),
FOREIGN KEY (SSN) REFERENCES Person
ON DELETE CASCADE
);
CREATE TABLE Insurance_Policy
(
policy_id VARCHAR(10),
provider_id VARCHAR(10),
provider_address VARCHAR(100),
insurance_type VARCHAR(10),
SSN VARCHAR(9),
PRIMARY KEY (policy_id),
FOREIGN KEY (SSN) REFERENCES Client,
);
CREATE TABLE Needs
(
SSN VARCHAR(9),
need_description VARCHAR(60),
importance_value INT CHECK(importance_value > 0 and importance_value <11),
PRIMARY KEY(SSN,need_description),
FOREIGN KEY(SSN) REFERENCES Client
ON DELETE CASCADE
);
Here is a screenshot if the formatting didn't hold up on procedure.
enter image description here

Answer 1

Based on your answers, I believe this is the code you are looking for. If this is not working, let me know.
To explain a little, using an INNER join will eliminate the need for a couple of those WHERE conditions. INNER JOIN only returns records where it exists in both tables. Also there is no need to link to the Client table from within the subquery.
Also you want where it does not have a description of transportation with an importance of less than 5. Since you are pulling a list to leave alone, you do not want to include these records.
DROP PROC IF EXISTS Option17;
GO
Create proc Option17
AS
BEGIN
DELETE FROM Client
WHERE SSN NOT IN (
SELECT
N.SSN
FROM Needs N
INNER JOIN Insurance_Policy I ON N.SSN = I.SSN
WHERE NOT (N.need_description = 'transportation' AND N.importance_value < 5)
);
END
GO

Answer 2

I think you want separate conditions on Needs and Insurance_Policy. And I recommend NOT EXISTS, because it better handles NULL values:
DELETE c
FROM Client c
WHERE NOT EXISTS (SELECT 1
FROM Insurance i
WHERE c.SSN = i.SSN
) AND
EXISTS (SELECT 1
FROM Needs n
WHERE c.SSN = n.SSN AND
n.need_description = 'transportation' AND
n.importance_value < 5
);