仅当该表中存在ID时才从表中选择mysql pdo php

Question

I want to create a select query using join on 3 or more tables. I have 3 tables namely t1 , t2 , t3 and a common column id existing in all 3 tables. I want to select the 3 table if the id exists in the table my query is like this.

Select * from t1 
inner join t2 on t1.id = t2.id 
inner join t3 on t2.id = t3.id 
where t1.id = 1 and t2.id = 1 and t3.id = 1

the query is returning values if the id exists in all the 3 tables. But if it is not in any table example t3 i will not return anything. I am looking for a way that if it does not exist in t3 it should i proceed to just select from t1 and t2

Answer 1

I think these sql wil helpful to you

Select * from t1,t2,t3 
where t1.id = 1 or t2.id = 1 0r t3.id = 1

these sql also will useful to you

SELECT * FROM t1 WHERE t1.id=1
UNION ALL
SELECT * FROM t2 WHERE t2.id=1
UNION ALL
SELECT * FROM t2 WHERE t2.id=1

Thank you.

Answer 2

Is this what you need?

SELECT * 
FROM t1 
INNER JOIN t2 on t1.id = t2.id 
LEFT JOIN  t3 on t2.id = t3.id 
WHERE t1.id = 1 AND t2.id = 1 AND (t3.id = NULL OR t3.id = 1)

Answer 3

SELECT * FROM t1 JOIN t2 ON t1.id = t2.id 
LEFT JOIN t2 ON t1.id= t2.id WHERE t1.id= 1

This will return null for t3 columns if id is not present in t3