Question

I’ve seen both used but I can’t seem to understand when to use each?

To me is seems like you enter the name of the table you are referring from in the ( ) and the field name in the [ ]?

Could anyone explain?

Answer 1

The square brackets are used In Microsoft products to specify that what’s within them is an identifier (the standard quoted identifiers are double quotes " ", which Microsoft SQL Sever also supports). This is used when you have a database name, user name, table name, field name, view name, procedure name (et.c.) that happens to be the same as a keyword, or contains characters that would break the syntax. This is often used in generated code to safeguard against identifiers that can’t otherwise be used in the code. A generated query could look like this:

select [Id], [Name], [Password hint]
from [dbo].[MyDataBase].[User]

Here the field name Password hint would break the syntax if used without brackets, and the table name User could conflict with the keyword User.

Parentheses are used to group items, for example as part of the syntax of some clauses, for example an insert:

insert into someTable (field1, field2) values ('value1', 'value2')

They can also be used in expressions:

select Price * (Quantity + FreeItems) from Articles

They can also be used around queries to make subqueries:

select o.Name
from (select Name, Age from Persons where City = 'Oslo') as o
where o.Age > 18