ALTER TABLE DROP CONSTRAINT

How to Resolve ORA-12991 Error Message

by Ed Chen
April 25, 2020December 20, 2022

ORA-12991: column is referenced in a multi-column constraint ORA-12991 means that the column you want to drop is bound to some multi-column constraints. You must… Read More »

How to Drop Primary Key in Oracle

by Ed Chen
April 22, 2020December 10, 2022

Drop Primary Key Primary key is sort of a constraint rather than an index, you should treat it as a constraint first so as to… Read More »

How to Resolve ORA-01400: cannot insert NULL into

by Ed Chen
November 27, 2019December 10, 2022
2 Comments

ORA-01400 ORA-01400 means that there's a column which was found as NOT NULL is not listed in the INSERT statement, you have to provide a… Read More »

How Oracle Remove NOT NULL Constraint

by Ed Chen
November 23, 2019November 3, 2022

Before we talk about how to remove NOT NULL constraint, I assume that you have already know how to add a NOT NULL constraint to… Read More »