Question

I am new to database.
my question is that i have created a table signUp whose columns are

id, first name, last name, email and country.

and i want to create a table named accout_recharge whose columns are (email,balance)
and whenever i insert a record into signup table the newly added email in the signup table also appear in account_recharge table using references or foreign key or whatever is required but without duplication.

Answer 1

you can try this

CREATE TABLE signup (
     id INT NOT NULL,
     firstName varchar(50),
     lastName varchar(50),
     countryName varchar(50),
     emailName varchar(50),
     PRIMARY KEY (id),
     index email_ind(emailName)    -- updated here 
) ENGINE=INNODB;


CREATE TABLE accout_recharge(  
    id INT,
    balance DECIMAL,
    email varchar(50),    
    FOREIGN KEY (email ) REFERENCES signup (emailName)
                      ON DELETE CASCADE
) ENGINE=INNODB;

MySql Foreign Key here you find more detail about foreign key reference

Update: I forget to tell you that foreign key reference always some kind of indexed column. so you need to turn you email column in an index. that why you are getting error: 150