[] brackets in sql statements

Question

What do the brackets do in a sql statement?

For example, in the statement:

insert into table1 ([columnname1], columnname2) values (val1, val2)

Answer 1

This is Microsoft SQL Server nonstandard syntax for "delimited identifiers." SQL supports delimiters for identifiers to allow table names, column names, or other metadata objects to contain the following:

• SQL reserved words: "Order"
• Words containing spaces: "Order qty"
• Words containing punctuation: "Order-qty"
• Words containing international characters
• Column names that are case-sensitive: "Order" vs. "order"

Microsoft SQL Server uses the square brackets, but this is not the syntax standard SQL uses for delimited identifiers. Standardly, double-quotes should be used for delimiters.

In Microsoft SQL Server, you can enable a mode to use standard double-quotes for delimiters as follows:

SET QUOTED_IDENTIFIER ON;