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Informix Error -594

-594 Cannot specify non-null default value for TEXT or BYTE column.

This CREATE or ALTER TABLE statement specifies that a column has a data type of BYTE or TEXT. It also has a DEFAULT clause for the column that specifies something other than NULL. You can only designate the default value NULL for columns of TEXT or BYTE data type.

Oninit® Troubleshooting Guidance

Reasons / Common Causes

-594 fires when a TEXT or BYTE (simple large object) column is given a DEFAULT clause specifying anything other than NULL — per the official guidance, NULL is the only value these two types can take as a default.

  1. A DEFAULT clause on a TEXT/BYTE column specifying a literal value, per the official guidance — the direct, only cause.
  2. DDL copy-pasted from a character or binary-string column's definition (which could legitimately default to a specific literal) into a TEXT/BYTE column's definition.
  3. A misunderstanding of TEXT/BYTE storage — these types store large data via a separate mechanism from ordinary column storage, which is why a literal default isn't supported the way it is for CHAR/VARCHAR.
Solutions / Resolution
  1. Change the default to NULL, per the official guidance — the only value these types accept as a default, or remove the DEFAULT clause entirely (which has the same effect).
  2. Populate the column explicitly on insert if a non-NULL initial value is genuinely needed, rather than relying on a DEFAULT clause.
Examples
The disallowed attempt
CREATE TABLE documents (doc_id INT, content TEXT DEFAULT 'placeholder');
-- -594: TEXT columns can only default to NULL
Corrected
CREATE TABLE documents (doc_id INT, content TEXT DEFAULT NULL);
Or populate explicitly on insert instead of relying on a default
INSERT INTO documents (doc_id, content) VALUES (1, 'actual content');
Diagnostic Checks
  1. Scan TEXT/BYTE column definitions for a DEFAULT clause specifying anything other than NULL, and change it to NULL or remove the clause.
Related Errors / Related Topics
  • -591 — "Invalid default value for column/variable column-name/variable-name." The more general DEFAULT-clause error family this specific TEXT/BYTE restriction belongs to.

TEXT/BYTE columns can only default to NULL — populate a non-NULL initial value explicitly on insert instead.