Informix Error -593: Cannot specify default value for SERIAL or SERIAL8 or BIGSERIAL column.

Cause and resolution

Cannot specify default value for SERIAL or SERIAL8 or BIGSERIAL column.

This CREATE or ALTER TABLE statement specifies that a column has a SERIAL or SERIAL8 or BIGSERIAL data type, but it also has a DEFAULT clause for the column. The database server generates values for a SERIAL or SERIAL8 or BIGSERIAL column each time a row is created, so the DEFAULT clause is meaningless.

Oninit® Troubleshooting Guidance

Reasons / Common Causes

-593 fires when a SERIAL, SERIAL8, or BIGSERIAL column is given a DEFAULT clause — per the official guidance, the server generates these columns' values automatically on every row insert, so a DEFAULT clause is meaningless for them.

A DEFAULT clause added to a SERIAL/SERIAL8/BIGSERIAL column definition, per the official guidance — the direct, only cause.
DDL copy-pasted from a non-serial column's definition (which legitimately had a DEFAULT clause) into a new serial column's definition, without removing the now-meaningless clause.
A misunderstanding of serial columns — expecting to need to specify a starting value via DEFAULT, when the starting value for a serial column is instead controlled by the initial value given in the type declaration itself (SERIAL(100), for instance).

Solutions / Resolution

Remove the DEFAULT clause from the serial column, per the official guidance — the server generates its values automatically; no DEFAULT is needed or accepted.
If a specific starting value is needed, set it in the type declaration itself, not via DEFAULT:
```
CREATE TABLE orders (order_id SERIAL(1000), status CHAR(10));
```

Examples

The disallowed attempt

CREATE TABLE orders (order_id SERIAL DEFAULT 1, status CHAR(10));
-- -593: SERIAL columns can't have a DEFAULT clause

Corrected — set the starting value in the type itself

CREATE TABLE orders (order_id SERIAL(1000), status CHAR(10));

Diagnostic Checks

Scan SERIAL/SERIAL8/BIGSERIAL column definitions for an attached DEFAULT clause and remove it, moving any intended starting value into the type declaration instead.

Related Errors / Related Topics

-591 — "Invalid default value for column/variable column-name/variable-name." The more general DEFAULT-clause error family this specific serial-column restriction belongs to.

DEFAULT is meaningless on auto-generated serial columns — set a starting value in the type declaration (SERIAL(n)) instead.