The database is a physical collection of files. Grouped into file
groups.
The database is logically a collection of tables. Grouped into
schema.
To bridge the gap between these entities: we use “file
groups"
File-groups is used to group one or more data files and
route table data.
Whenever we define a database one file-group is auto-created:
"primary file-groups"
Syntax for table creation:
Create
table <schema name>.<table name>
(
Column
name <type> <constraint>,
Column
name <type> <constraint>,
Column
name <type> <constraint>,
Column
name <type> <constraint>,
......
)
On
file group name
Only one primary key is possible per table.
No
limit on a number of unique & foreign keys.
Purpose of file groups: easy data allocation + performance
tuning +Easy recovery
Purpose of schema:- easy security management
Default schema is dob = database owner.
Default file group is primary.
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