Full outer join and Left outer join

Union All is faster than union in SQL Server

#

Stored procedures allow a lot more flexibility offering capabilities such as conditional logic
Stored procedures are stored within the DBMS, bandwidth and execution time are reduced
Client developers are abstracted from complex designs

1. A UNIQUE constraint is similar to PRIMARY key, but you can have more than one UNIQUE constraint per table.
2. Primary Key does not allow null values whereas unique constraint allows 'single' null value.
3. A table can have only single Primary Key where as it can have multiple unique constraints ( max 16)
4. Primary Key creates clustered index by default whereas Unique Key creates non-clustered index by default

UNION: OR operator (value is selected if it appears in either the first or the second statement)
INTERSET:AND operator (value is selected only if it appears in both statements).

UNION : Doesn't return Duplicate Values.
UNION ALL: return All values (includes Duplicate Values)

Top: Retrieve Top records from the Table,
LIMIT: Retrieve LIMIT records from the Table.

constraint:
protect columns of the table from unwanted values.
NOT NULL, CHECK, UNIQUE, PRIMARY KEY, FOREIGN KEY are the types of contraints define in SQL Server.

Primary Key:
A column defined as primary key doesn’t allow null value.
By default, clustered index in created with the column having primary key.
Unique Key:
A column with unique key defined allows null value.
By default, it creates non-clustered index.