Question

i am having three tables namely

1)cd_register

|----------------------------------------------------|
|   username  |  name   |  age   | sex   | dob       |
|----------------------------------------------------|

2)cd_social

|-------------------------------------|
|   username  |  religion  |  caste   |
|-------------------------------------|

and
3)cd_professional

|----------------------------------------|
|   username  | occupation | education   |
|----------------------------------------|

now i’m using this query in mysql but its giving error

SELECT cd_register.name, cd_register.age, cd_register.dob, cd_social.religion, cd_social.caste, cd_professional.profession
FROM cd_register, cd_social,cd_professional
WHERE 
cd_register.sex = 'Male',
cd_social.religion = 'Hindu',
cd_social.caste = 'Brahmin',
cd_professional.occupation = 'Doctor',
cd_register.username = cd_social.username AND
cd_register.username = cd_professional.username 

now i want to mention that username is the primary key of all the tables. Also
username of cd_register is foreign key in cd_social. Also
username of cd_register is foreign key in cd_professional.

Answer 1

You can use join

SELECT t1.name, t1.age, t1.dob, t2.religion, t2.caste, t3.profession
FROM cd_register as t1
LEFT JOIN cd_social as t2 
ON t1.username = t2.username and t2.caste = 'Brahmin' and t2.religion ='Hindu'
LEFT JOIN cd_professional as t3 
ON t1.username = t3.username and t3.occupation = 'Doctor' 
WHERE t1.sex = 'Male'