MySQL database schema: 3 columns of same type with different purpose - mysql

Question

I am building a financial app, and it requires the following tables:
tax
item, which can have one tax
invoice, which can have many items
To the question:
An invoice must have the ability to contain 3 categories of emails:
Recipient emails
CC emails
BCC emails
So far I just have a recipients/cc/bcc column, but I don't think it's good because I'd basically have to concatenate the emails together and separate them by a comma or something.
I also thought about a generic email table, but then I'd have to create invoice_recipient_email, invoice_cc_email and invoice_bcc_email tables respectively, in order to link the emails back to the particular invoice ID as well as categorize them by the 3 types.
Can someone advice me on my second solution, or provide a better way to do this?
Here is my current schema:
CREATE TABLE tax (
id INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
name VARCHAR(255) NOT NULL,
rate INT(3) NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE item (
id INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
name VARCHAR(255) NOT NULL,
description VARCHAR(1000) NOT NULL,
quantity INT(10) NOT NULL,
price INT(10) NOT NULL,
CONSTRAINT `f_tax_item_tax_id` FOREIGN KEY (`tax_id`) REFERENCES `tax` (`id`),
PRIMARY KEY (id)
);
CREATE TABLE invoice (
id INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
invoice_number VARCHAR(255) NOT NULL,
recipients VARCHAR(1000) NOT NULL,
cc VARCHAR(1000) NOT NULL,
bcc VARCHAR(1000) NOT NULL,
discount INT(10) NOT NULL,
note VARCHAR(500) NOT NULL,
terms VARCHAR(2000) NOT NULL,
due_date TIMESTAMP NOT NULL,
PRIMARY KEY (id)
);

Answer 1

I would add a single recipients table with id (pk), invoice_id (fk), email, recipient_type fields, where recipient type could have one of the following values: to, cc, or bcc. The recipient type field would tell you how to use the email address, therefore you would not need 3 separate tables to hold the 3 different recipient types.
1 record would hold only 1 email address.

Answer 2

You can normalize your emails into a single table and put a flag on it to categorize its type.
CREATE TABLE invoice (
id INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
invoice_number VARCHAR(255) NOT NULL,
discount INT(10) NOT NULL,
note VARCHAR(500) NOT NULL,
terms VARCHAR(2000) NOT NULL,
due_date TIMESTAMP NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE email(
id INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
invoice_id INT(10) not null references invoice(id),
email_type int not null,
addresses varchar(1000),
PRIMARY KEY (id)
);
You can define your email types in another table as well. You can look at this approach implemented in a production environment for phone numbers in MSSSQL but same concept. We however normalize the records to one phone number per record which I would also recommend you do.
CREATE TABLE [dbo].[ActorPhones](
[PKId] [int] IDENTITY(0,1) NOT NULL Primary Key,
[FKActorId] [int] NOT NULL References Actor(PKID),
[FKPhoneTypeId] [int] NOT NULL,
[Number] [varchar](20) NOT NULL
) ON [PRIMARY]
CREATE TABLE [dbo].[PhoneTypes](
[PKId] [int] IDENTITY(0,1) NOT NULL Primary Key,
[PhoneTypeName] [varchar](50) NOT NULL References ActorPhones(PKId),
[PhoneTypeDescription] [varchar](250) NULL,
[ModifiedDate] [datetime] NULL,
[ModifiedBy] [varchar](50) NULL
)