The string operator + can be used to concatenate two or more character or binary expressions. For example, the following displays author names under the column heading Namein last-name first-name order, with a comma after the last name; for example, “Bennett, Abraham.”:
select Name = (au_lname + ", " + au_fname) from authors
The following returns the string “abc def”. The empty string is interpreted as a single space in all char, varchar, unichar, nchar, nvarchar, and text concatenation, and in varchar and univarchar insert and assignment statements:
select "abc" + "" + "def"
When concatenating non-character, non-binary expressions, always use convert:
select "The date is " + convert(varchar(12), getdate())
A string concatenated with NULL evaluates to the value of the string. This is an exception to the SQL standard, which states that a string concatenated with a NULL should evaluate to NULL.