Concatenation 

A concatenation x||y or x&y is a string function that supplies the following results for character string x (string specification with the length n) and character string y (string specification with the length m):

	Result of the concatenation
x||y or x&y	x and y are concatenated to a character string with the length n+m. If a character string originates from a column, its length is determined without taking trailing blanks into account (code attribute. ASCII, UNICODE) or binary zeros (code attribute BYTE).
x or y is the NULL value	NULL value

Examples

SQL Tutorial, Functions, Changing character strings

Explanation

Only expressions that produce an alphanumeric value are permitted as string specifications.

Columns with the same code attribute can be concatenated.

Columns with different code attributes (ASCII and UNICODE) can be concatenated together and with date values, time values, and timestamp values.