Informix Error -362

-362 Can have only one column of serial/(serial8 or bigserial) type.

A table can have at most only one column of type SERIAL and one column of type SERIAL8/BIGSERIAL. You are attempting to add a second column of type SERIAL or SERIAL8/BIGSERIAL, or you are attempting to create a table with more than one column of either type. If you intended to have a foreign key (that is, a column that refers to a SERIAL or SERIAL8/BIGSERIAL column in a different table), the data type of the column in this table should be INTEGER or INT8 or BIGINT.

Oninit® Troubleshooting Guidance

Reasons / Common Causes

-362 is a per-table cardinality limit: a table can have at most one SERIAL column and, separately, at most one SERIAL8/BIGSERIAL column — not two of the same auto-incrementing type. This trips people up most often when a foreign key column is mistakenly declared as SERIAL too, since a foreign key referencing a SERIAL primary key should use a plain integer type instead.

A CREATE TABLE/ALTER TABLE ADD attempting a second SERIAL (or second SERIAL8/ BIGSERIAL) column on the same table — the direct cause.
Declaring a foreign key column as SERIAL when it should be INTEGER/INT8/BIGINT — a foreign key only needs to hold values matching the referenced SERIAL column's generated numbers, not generate its own.
Copy-pasted column definitions carried over from the primary key column's SERIAL declaration into a different column that shouldn't auto-increment.

Solutions / Resolution

Use INTEGER, INT8, or BIGINT for a foreign key referencing a SERIAL column, per the official guidance — never SERIAL itself on the referencing side.
Confirm only one column is intended to auto-generate values per table, and use a sequence-based or application-managed value for any additional "unique identifier" columns instead of a second SERIAL.

Examples

A foreign key mistakenly declared as SERIAL

CREATE TABLE customers (
    customer_id SERIAL PRIMARY KEY,
    name VARCHAR(50)
);

CREATE TABLE orders (
    order_id SERIAL PRIMARY KEY,
    customer_id SERIAL REFERENCES customers(customer_id)
);
-- -362: orders already has order_id as SERIAL

Fix — use a plain integer type for the foreign key column:

CREATE TABLE orders (
    order_id SERIAL PRIMARY KEY,
    customer_id INTEGER REFERENCES customers(customer_id)
);

Diagnostic Checks

Review the table's column definitions for more than one SERIAL column, or more than one SERIAL8/BIGSERIAL column.
For any foreign key column, confirm it uses a plain integer type, not SERIAL, regardless of what type the referenced column uses.

Related Errors / Related Topics

-356 — "Data type of the referencing and referenced columns do not match." A closely related concern — the correct type for a foreign key column referencing a SERIAL column is a plain integer type, which also needs to match on both sides.
-328 — "Column column-name already exists in table." Another ALTER TABLE ADD-time restriction, though about naming rather than type cardinality.

A foreign key referencing a SERIAL column should always be declared as a plain INTEGER/ INT8/BIGINT, never SERIAL itself — that's the most common way this limit gets hit.