#1452 - Cannot add or update a child row: a foreign key constraint fails (`Appian`.`#sql-alter-34ce-15086d9`, CONSTRAINT `table1_ibfk_2` FOREIGN KEY (`first_id`) REFERENCES `table2` (`first_id`))

What does this error mean?

Question

#1452 - Cannot add or update a child row: a foreign key constraint fails (`Appian`.`#sql-alter-34ce-15086d9`, CONSTRAINT `table1_ibfk_2` FOREIGN KEY (`first_id`) REFERENCES `table2` (`first_id`)) 
 
 What does this error mean?

Shyam Bommakanti · Answer

Seems like a FK constraint issue. 
 In cloud DB select your table and see the FK constraints and verify you are sending the correct data to your fk

Selvakumar Kumarasamy · Answer

shubhamy0001 
 Since you are getting this error while creating the relationship itself, I think your foreign key column contains values that are not present in the parent table as a primary key. 
 For example, let's say tableA is the parent table & the primary key column is colA. It contains 10 rows of data hence the primary key values are 1,2,3,4,5,6,7,8,9,10. Your child table is tableB & the foreign key column is colB . If the colB has values other than the present values such as 0 (or) greater than 10, then the database will not allow adding the constraint because it fails. 
 Try deleting such values from your child table & then perform this operation.

bharathkumarr0001 · Answer

Hi Shubha,

You can find the rows present in the child table that is causing the conflict while establishing the foreign key constraint by using the below query:

(Please change the table name and column name according to your scenario)

SELECT * FROM childTable WHERE childTablePrimaryKey IN
(SELECT childTablePrimaryKey from childTable WHERE NOT EXISTS
(Select 1 from parentTable where parentTable.foreignkeyColumn = childTable.foreignkeyColumn)
) AND foreignkeyColumn IS NOT NULL;

The result of above query will give you the conflicting rows and please try deleting those rows and then execute the foreign key creation query.

Ravi Roshan · Answer

If you are establishing the FK relation while creating the CDT, please make sure you provide the fk column name all in small(the column name to be mapped).

#1452 - Cannot add or update a child row: a foreign key constraint fails (`Appian`.`#sql-alter-34ce-15086d9`, CONSTRAINT `tems_stability_ranges_ibfk_2` FOREIGN KEY (`budget_id`) REFERENCES `tems_etem_log_excursion` (`budget_id`))

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