Meaning of square brackets [] in MS-SQL table designer? [duplicate]

Answer 1

Square brackets may be placed around objects (e.g. views, databases, columns etc)

Their primary purpose is, as Mark mentioned, to encapsulate the objects so that special characters such as a space or period do not interfere with your syntax.

Many applications by default use the bracketed notation, to further reduce risk of syntax errors or anything of that sort.

It's typically good practice to not include any spaces

Database_Name < GOOD PRACTICE

Database Name < GENERALLY TRY TO AVOID

In any case, if the latter is used, you may use square brackets i.e.

select * from [Database Name]

Answer 2

The square brackets [] are used to delimit identifiers. This is necessary if the column name is a reserved keyword or contains special characters such as a space or hyphen.

Some users also like to use square brackets even when they are not necessary.

From MSDN:

Delimited identifiers

Are enclosed in double quotation marks (") or brackets ([ ]). Identifiers that comply with the rules for the format of identifiers may or may not be delimited.

SELECT *
FROM [TableX]         --Delimiter is optional.
WHERE [KeyCol] = 124  --Delimiter is optional.

Identifiers that do not comply with all of the rules for identifiers must be delimited in a Transact-SQL statement.

SELECT *
FROM [My Table]      --Identifier contains a space and uses a reserved keyword.
WHERE [order] = 10   --Identifier is a reserved keyword.

Answer 3

the brackets are special characters in sql server that are used to explicitly delimit information.

they can be used in xml as per the article, they can also be used to specify meta names (column, table, etc.) that have spaces or other key words.

declare my column nvarchar(50)

would be invalid syntax, but you could do

declare [my column] nvarchar(50)

just think of them as explicit delimiters.