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I'v kind of login system where user add each other but when both users add each other we want to show them in different format/color.
For example:A user is logged In and want to add others.
If the currently logged in user adds someone into the system who has also added this currently logged In user then we want to show both of them in different format.

Will become clear from the following scenario.

I'v two table one is user user, and the second is userdata userdata.
Column id is primary key in user and Foreign key in userdata as adder.
I want to insert the data into the table called user when the structure is something like this.

user

 id name

 1 Alice
 2 Bob
 3 jhon

userdata

 adder added
 1 2
 1 3

the userdata table shows that the user Alice has added Bob and Alice added jhon so whenever there is already a relation in userdata like

 1 2 i.e (**Alice added Bob**)

and when there is second row populated from front end that says

 2 1 i.e (**Bob added Alice**)

so when this happens i.e Alice added Bob and vice versa I want to insert them in to the DB and show them in different way.How to take decision when Alice Added Bob and Bob Added Alice.

A JOIN is what you are looking for.

If you want to know who added who, you can use this query

Schema (MySQL v5.7)

CREATE TABLE users
(
 id INT(6) AUTO_INCREMENT NOT NULL PRIMARY KEY,
 name VARCHAR(255)
);

CREATE TABLE userdata
(
 adder INT(6) NOT NULL,
 added INT(6) NOT NULL,
 CONSTRAINT adder_user FOREIGN KEY (adder) REFERENCES users(id),
 CONSTRAINT added_user FOREIGN KEY (added) REFERENCES users(id),
 PRIMARY KEY (adder, added)
);

INSERT INTO users VALUES (default, "Alice"), (default, "Bob"), (default, "John");

INSERT INTO userdata VALUES (1, 2), (1, 3), (2, 3), (2, 1);

Query #1

SELECT aer.name AS Adder, 'added' AS Action, aed.name AS Added
FROM users aer
INNER JOIN userdata ud ON aer.id = ud.adder
INNER JOIN users aed ON aed.id = ud.added
WHERE
(
 SELECT COUNT(*)
 FROM userdata uda
 WHERE uda.adder = ud.added
 AND uda.added = ud.adder
) >= 1;

Outputs :

| Adder | Action | Added |
| ----- | ------ | ----- |
| Bob | added | Alice |
| Alice | added | Bob |

View on DB Fiddle