Day 4


1: What is the relationship between table and entity?
A1: A table contains information about an entity. An entity can be a person, a thing, a place, or an event.
2: What is NULL?
A2: NULL is a special value used to identify a missing value. You specify which columns can accept NULL values. Primary keys cannot contain NULLs.
3: What are other names for record and field?
A3: Another name for record is row. Another name for field is column.
4: True/False. A primary key can only contain one column.
A4: False. A primary key can contain many columns (in SQL Server, a primary key cannot exceed 256 bytes), although most tables have a primary key with a single column.
5: What's a foreign key?
A5: A foreign key occurs when a table has a ...

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