Concatenates one-dimensional ARRAY data types.
The result of the concatenation operation is a new 1-D ARRAY value of the same type as the data type of the two arguments, where all of the elements present in array_expr1 are followed by all the elements that are present in array_expr2. Elements that are present include NULL elements, but do not include elements that are in an uninitialized state.
Since the result value and the argument values are of the same 1-D ARRAY type, they have the same maximum size n. Therefore, if the number of elements that results from the concatenation of array_expr1 and array_expr2 is greater than the maximum size n of the defined 1-D ARRAY type, the operation will abort with an error.
If either argument is NULL, the result of the operation is NULL.
The ARRAY concatenation operator cannot be used with multidimensional ARRAY data types.
The ARRAY concatenation operator for one-dimensional (1-D) ARRAY data types is partially ANSI SQL:2011 compliant.
The ARRAY concatenation operator requires that both operands are instances of the same ARRAY type and that the target type of the concatenation operation is also the same type. This is a deviation from the ANSI standard because it defines the target data type of a 1-D ARRAY concatenation to be a new 1-D ARRAY type with the length defined as the sum of the length of both operands.