Using SERIAL8 and BIGSERIAL with INT8 or BIGINT

All the arithmetic operators that are valid for INT8 and BIGINT (such as +, -, *, and /) and all the SQL functions that are valid for INT8 and BIGINT (such as ABS, MOD, POW, and so on) are also valid for SERIAL8 and BIGSERIAL values.

Data conversion rules that apply to INT8 and BIGINT also apply to SERIAL8 and BIGSERIAL, but with a NOT NULL constraint on SERIAL8 or BIGSERIAL.

The value of a SERIAL8 or BIGSERIAL column of one table can be stored in INT8 or BIGINT columns of another table. In the second table, however, the INT8 or BIGINT values are not subject to the constraints on the original SERIAL8 or BIGSERIAL column.