Informix Error -593

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.