How To Identify An Array

I have seen several examples explaining the fact that a table
containing a field for each day of the week is for the most part an
array. An specific example is where data representing worked hours is
stored in a table.

CREATE TABLE [hoursWorked] (
[id] [int] NOT NULL ,
[location_id] [tinyint] NOT NULL,
[sunday] [int] NULL ,
[monday] [int] NULL ,
[tuesday] [int] NULL ,
[wednesday] [int] NULL ,
[thursday] [int] NULL ,
[friday] [int] NULL ,
[saturday] [int] NULL
)

I had to work with a table with a similar structure about 7 years ago
and I remember that writing code against the table was pretty close to
Hell on earth.

I am now looking at a table that is similar in nature - but different.

CREATE TABLE [blah] (
[concat_1_id] [int] NOT NULL ,
[concat_2_id] [int] NOT NULL ,
[code_1] [varchar] (30) NOT NULL ,
[code_2] [varchar] (20) NULL ,
[code_3] [varchar] (20) NULL ,
[some_flg] [char] (1) NOT NULL
) ON [PRIMARY]

The value for code_2 and code_3 will be dependently null and they will
represent similar data in both records (i.e. the value "abc" can exist
in both fields) . For example if code_2 contains data then code_3 will
probably not contain data.

I do not think that this is an array. But with so many rows where
code_2 and code_3 will be NULL something just does not feel right.

I will appreciate your input.