Editing First normal form (section)

===Design that violates 1NF===
This table of customers' credit card transactions does not conform to first normal form, as each customer corresponds to a repeating group of transactions. Such a design can be represented in a [[hierarchical database]], but not in an SQL database, since SQL does not support nested tables. 

{{Table alignment}}
{| class="wikitable col1right"
|+ Customer
! <u>CustomerID</u> !! Name !! Transactions
|-
| 1 || Abraham
||
{{Table alignment}}
{| class="wikitable col1right col3right"
! <u>TransactionID</u> !! Date !! Amount
|-
| 12890 || 2003-10-14 || &minus;87
|-
| 12904 || 2003-10-15 || &minus;50
|}
|-
| 2 || Isaac
||
{{Table alignment}}
{| class="wikitable col1right col3right"
! <u>TransactionID</u> !! Date !! Amount
|-
| 12898 || 2003-10-14 || &minus;21
|}
|-
| 3 || Jacob
||
{{Table alignment}}
{| class="wikitable col1right col3right"
! <u>TransactionID</u> !! Date !! Amount
|-
| 12907 || 2003-10-15 || &minus;18
|-
| 14920 || 2003-11-20 || &minus;70
|-
| 15003 || 2003-11-27 || &minus;60
|}
|}

The evaluation of any query relating to customers' transactions would broadly involve two stages:
# unpacking one or more customers' groups of transactions, allowing the individual transactions in a group to be examined, and
# deriving a query result from the results of the first stage.

For example, in order to find out the monetary sum of all transactions that occurred in October 2003 for all customers, the [[database management system]] (DMBS) would have to first unpack the Transactions field of each customer, then sum the Amount of each transaction thus obtained where the Date of the transaction falls in October 2003.