DP-900 · 2 Identify considerations for relational data on Azure
Relational data model
Exam objective: Identify features of relational data
A relational database models real world entities as tables, where each row is one instance and each column holds one attribute with its own data type.
A relational database represents real world things, such as customers, products, orders and the items inside an order, as separate tables. Each table models one type of entity, and every row in that table is one instance of it: one row per customer, one row per order.
Each column holds a single attribute of the entity, and every row in the table has the same set of columns. A column does not need a value in every row. A customer table might include a MiddleName column that stays empty, or NULL, for a customer who has no middle name. The column still exists, so the schema has not changed.
Every column stores one data type, such as character text, a whole number, a decimal number or a date and time value. The exact data types a database system offers can vary, but many systems support a shared set of standard types.
On the exam, look for a description of entities split into tables, with rows as instances and columns as typed attributes.
Key points
- A table represents one type of entity, such as customers, products or orders.
- Each row in a table is a single instance of that entity, and each column is one attribute of it.
- Every row shares the same columns, but a column can be empty (NULL) for a row where it does not apply.
- Each column stores values of one data type, such as character text, a decimal number, an integer or a date and time.
Exam trap
A table with an empty value in some rows, such as an optional middle name, is still structured. The schema stays fixed because the column exists for every row, even when its value is missing.
Check yourself
For each statement about a relational table, select Yes if it is true. Otherwise, select No.
- Every row in a table must contain a value in every column.
- All rows in the same table share the same set of columns.
- A single column can store more than one data type at the same time.
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Checked against Microsoft Learn on October 1, 2026.