The query is not giving a desired output which I want - mysql

Question

Query with OR which outputs wrong
SELECT DISTINCT
sm___employees.id,
sm___employees.employee_code,
sm___employees.leaving_date,
sm___employees.name_of_employee,
sm___employees.position,
sm___employees.rating,
sm___employees.entry_date
FROM
sm___employees
JOIN
sm___employee_skills
ON
sm___employees.id=sm___employee_skills.employee_id
WHERE
((sm___employee_skills.skill_id=1 AND sm___employee_skills.ans LIKE '%MBA%')
**OR**
(sm___employee_skills.skill_id=5 AND sm___employee_skills.ans IN (3)))
AND
sm___employees.rating IN (1)
ORDER BY
sm___employee_skills.date DESC
But I want it by And
SELECT DISTINCT
sm___employees.id,
sm___employees.employee_code,
sm___employees.leaving_date,
sm___employees.name_of_employee,
sm___employees.position,
sm___employees.rating,
sm___employees.entry_date
FROM
sm___employees
JOIN
sm___employee_skills
ON
sm___employees.id=sm___employee_skills.employee_id
WHERE
((sm___employee_skills.skill_id=1 AND sm___employee_skills.ans LIKE '%MBA%')
**AND**
(sm___employee_skills.skill_id=5 AND sm___employee_skills.ans IN (3)))
AND
sm___employees.rating IN (1)
ORDER BY
sm___employee_skills.date DESC
When am using first query with OR of MBA or 3, It gives me result for both which is correct as per OR operation
I want only those records which are having MBA AND 3 which gives me blank records when there are records available with this comparison
So please help me to resolve this.
Thank you in advance

Answer 1

To start with: DISTINCT often indicates a badly written query. This is the case here. You are joining records only to dismiss them later. If you want employee records, then select from the employee table. If you have criteria on the skills table check this in the WHERE clause. Don't join.
Then the WHERE clause looks at one row at a time. So neither skill_id = ... AND skill_id = ... nor skill_id = ... OR skill_id = ... can work for you. You must look up the skills table twice:
SELECT
id,
employee_code,
leaving_date,
name_of_employee,
position,
rating,
entry_date
FROM sm___employees
WHERE rating IN (1)
AND id IN
(
SELECT employee_id
FROM sm___employee_skills
WHERE skill_id = 1 AND ans LIKE '%MBA%'
)
AND id IN
(
SELECT employee_id
FROM sm___employee_skills
WHERE skill_id = 5 AND ans IN (3)
);
And here is a way to look up skills just once:
SELECT
id,
employee_code,
leaving_date,
name_of_employee,
position,
rating,
entry_date
FROM sm___employees
WHERE rating IN (1)
AND id IN
(
SELECT employee_id
FROM sm___employee_skills
WHERE (skill_id = 1 AND ans LIKE '%MBA%')
OR (skill_id = 5 AND ans IN (3))
GROUP BY employee_id
HAVING COUNT(DISTINCT skill_id) = 2 -- both skills
);
It seems strange though that you consider ans to be a string in one place (ans LIKE '%MBA%') and a number in another (ans IN (3)).
UPDATE: If you want to sort by skill date, you should consider by which skill's date. For this to happen, you would join, but not join the skills table, but the skills aggregate result. E.g.:
SELECT
e.id,
e.employee_code,
e.leaving_date,
e.name_of_employee,
e.position,
e.rating,
e.entry_date
FROM sm___employees e
JOIN
(
SELECT employee_id, MAX(date) AS max_date
FROM sm___employee_skills
WHERE (skill_id = 1 AND ans LIKE '%MBA%')
OR (skill_id = 5 AND ans = 3)
GROUP BY employee_id
HAVING COUNT(DISTINCT skill_id) = 2 -- both skills
) s ON s.employee_id = e.id
WHERE e.rating = 1
ORDER BY s.max_date;

Answer 2

Please try this :
SELECT DISTINCT
sm1.id,
sm1.employee_code,
sm1.leaving_date,
sm1.name_of_employee,
sm1.position,
sm1.rating,
sm1.entry_date
FROM sm___employees sm1
LEFT JOIN sm___employee_skills sm2 ON sm1.id = sm2.employee_id
WHERE ((sm2.skill_id=1 AND sm2.ans LIKE '%MBA%')
AND (sm2.skill_id=1 AND sm2.ans=3))
AND sm1.rating IN (1)
ORDER BY sm2.date DESC;