How to create a table such that when ever a record is inserted, composite key values gets inserted in another column?

Question

I could find many methods to create a unique composite key while creating a table. But I was unable to figure out how i can create a column that contains composite key values automatically whenever a record is inserted.

For example.

if I

insert ('pine','apple') into Fruits

I want the table to be

name1   name2   fullname
------------------------
pine    apple   pine apple

my create statement.

create table ( column_names,
primary key(name1,name2));

What changes do i have to make to my create statement to achieve this ? Thanks in advance.

Answer 1

Use generated column:

CREATE TABLE mytable ( name1 VARCHAR(127) NOT NULL,
                       name2 VARCHAR(127) NOT NULL,
                       fullname VARCHAR(255) AS (CONCAT(name1, ' ', name2)) STORED,
                       PRIMARY KEY(fullname) );
-- or
CREATE TABLE mytable ( name1 VARCHAR(127) NOT NULL,
                       name2 VARCHAR(127) NOT NULL,
                       fullname VARCHAR(255) AS (CONCAT(name1, ' ', name2)) VIRTUAL,
                       PRIMARY KEY(name1, name2) );

Remember - you cannot set the value to generated column explicitly (in INSERT or UPDATE). Either skip it from columns list or use DEFAULT keyword for its value.