# SQLCODE -538: Foreign key doesn't match parent key

Source: https://wndsoftware.com/mainframe-errors/sqlcode-538

### SQLCODE -538: Foreign key doesn't match parent key

SQLCODE -538 (SQLSTATE 42830) means a FOREIGN KEY definition doesn't match a parent key of the table it references. The parent columns aren't a primary key or unique key, or the two keys differ in column count, data type, length or field procedure.


#### Other names for this code

Also written as `SQL -538`, `SQLCODE=-538`, `SQLCODE = -538`, `db2 -538`, `sqlstate 42830`, `SQL0538N`, `foreign key does not conform to the description of a parent key`.


### What it means

A referential constraint links a foreign key in a child table to a parent key in another table. You define it in CREATE TABLE or ALTER TABLE with `FOREIGN KEY (cols) REFERENCES parent (cols)`. If REFERENCES lists no columns, Db2 uses the parent's primary key.

Db2 checks two things before it accepts the constraint. The parent columns must be the primary key or a unique key of the parent table. And the foreign key must describe the same key, column for column, in order. That means the same number of columns, the same data types, the same lengths and the same field procedures. If either check fails, Db2 rejects the statement with -538.

For temporal tables there's one more rule. PERIOD BUSINESS_TIME has to appear on both keys or on neither, and the period must mean the same thing in both tables.

The token in the message is the constraint name. If the FOREIGN KEY clause had no constraint name, Db2 shows the first column of the foreign key instead.


### Common causes

- The REFERENCES clause points at columns that aren't a primary key or unique key of the parent, for example a code column that only has a non-unique index.
- The data types differ, such as INTEGER in the child and DECIMAL(9,0) in the parent, or CHAR(8) against CHAR(10), or CHAR against VARCHAR.
- The columns are listed in a different order from the parent key, so the first child column is compared with the wrong parent column.
- The foreign key has more or fewer columns than the parent key.
- One column uses a field procedure and the other doesn't.
- PERIOD BUSINESS_TIME is on one key and not the other.


### How to find the problem

- Take the constraint or column name from the message and find the FOREIGN KEY clause in the DDL.
- List the parent's keys. `SELECT CONSTNAME, TYPE FROM SYSIBM.SYSTABCONST WHERE TBCREATOR = 'PROD' AND TBNAME = 'CUSTOMER'` shows primary (P) and unique (U) constraints, and SYSIBM.SYSKEYCOLUSE lists their columns in order. Columns with KEYSEQ greater than zero in SYSIBM.SYSCOLUMNS make up the primary key.
- Compare COLTYPE, LENGTH and SCALE in SYSIBM.SYSCOLUMNS for each pair of columns, child against parent, in key order.


### How to fix it

- Point REFERENCES at the parent's primary key or at a unique key, and list the columns in the same order as that key.
- If the parent columns should be a key but aren't, have the DBA create the unique index and add a UNIQUE constraint on them first.
- Change the child column definitions so their types and lengths match the parent exactly. On a table that already holds data that may mean ALTER COLUMN SET DATA TYPE, or re-creating the table.
- Keep key columns defined from one shared copy of the data model so the child and parent can't drift apart.


### What it looks like


```text
DSNT408I SQLCODE = -538, ERROR:  FOREIGN KEY ORDCUSTFK DOES NOT CONFORM TO THE DESCRIPTION OF A PARENT KEY OF TABLE PROD.CUSTOMER
DSNT418I SQLSTATE   = 42830 SQLSTATE RETURN CODE
```


### IBM documentation

[IBM documentation: -538](https://www.ibm.com/docs/en/db2-for-zos/13.0.0?topic=codes-538). Use the documentation for your installed release.

[Report a correction to WND Software](https://wndsoftware.com/contact#message).

Technical reviewer: [Albert Joseph](https://wndsoftware.com/authors/albert-joseph), WND Software.

Last reviewed 2026-10-18 by the WND Software team. Written in our own words. For the full reference, check IBM’s Db2 for z/OS documentation for your release.


### Related codes

[SQLCODE -530 Foreign key value has no parent Read →](https://wndsoftware.com/mainframe-errors/sqlcode-530)
[SQLCODE -532 Delete restricted by a foreign key Read →](https://wndsoftware.com/mainframe-errors/sqlcode-532)
[SQLCODE -540 Table definition incomplete, missing index Read →](https://wndsoftware.com/mainframe-errors/sqlcode-540)
[SQLCODE -542 Key column allows nulls Read →](https://wndsoftware.com/mainframe-errors/sqlcode-542)
[SQLCODE -624 Table already has a primary key Read →](https://wndsoftware.com/mainframe-errors/sqlcode-624)

### Questions


#### Do the column names have to match?

No. Db2 compares the columns by position, data type, length and field procedure. The names can differ.


#### Is -538 the same on Db2 for LUW?

Yes. Db2 for LUW reports SQL0538N with SQLSTATE 42830 for the same mismatch.


#### What is the difference between -538 and -530?

-538 is a DDL error, raised when the constraint is defined. -530 comes later, when an INSERT or UPDATE puts a foreign key value in the child table that has no matching parent row.

[Db2 SQLCODEs](https://wndsoftware.com/mainframe-errors/db2-sqlcodes) · [SQLCODE -532](https://wndsoftware.com/mainframe-errors/sqlcode-532) · [SQLCODE -540](https://wndsoftware.com/mainframe-errors/sqlcode-540)

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