constraints

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Unique Constraint vs Unique Index in Oracle

A unique constraint and a unique index, on the face of it, look very alike. Dig deeper, and you will see that they differ. A rundown of unique constraint vs unique index in Oracle.

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Replace Duplicates in ID Column with Unique Values

A solution to the requirement of replacing only the duplicate IDs with unique values in a database table, and letting everything else stay untouched.

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Delete Old Data from Database Schema

How to Delete Old Data from the Entire Schema

We may want to slim down a database schema, pruning old data from all tables, for a number of reasons. Let’s say to set up the test environment for a data migration project, a replica of the legacy database schema has been created. The legacy database schema has millions of records spanning multiple years, but […]

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Passing Parameter by Value

NOCOPY Parameter Hint in PL/SQL

Before we get to understanding the NOCOPY parameter hint in PL/SQL, it would help to first look at PL/SQL parameter modes and the ways in which they pass values in and out of a subprogram. PL/SQL subprograms have three parameter modes:

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10 Important Lessons in Data Modeling

Follow these ten data modeling guidelines to make sure that your application database design is accurate, usable and scalable.

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Drop and Recreate All Foreign Keys on Oracle Table

You might need to reistate a dropped table in Oracle, and in doing so, restore the foreign keys as well. Here’s how to drop and recreate all foreign keys on an Oracle table.

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ORA-02449: Solving the DROP TABLE Dilemma

Quick workaround to error ORA-02449. When you want to drop and recreate an Oracle table, but Oracle does not let you do so due to foreign key references.

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Alter Table Add Table Column at Specific Position

How to Add Table Column at Specific Position

In a perfect world, the database design is firm and final before development starts. But we do not live in a perfect world – changes can and do happen. You forgot a column in a table, or your client has a change request – for various reasons, you may find that you need to add […]

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Oracle Views

20 Things You Should Know About Oracle Views

A view is like a virtual table. It takes the output of a query and treats it like a table. A view can be based on one or more tables or other views. These tables/views are called base tables. A view takes up no storage space other than for the definition of the view in […]

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delete-truncate-drop

The Difference between DELETE, TRUNCATE and DROP

DELETE, TRUNCATE and DROP – all three commands get rid of table data. How exactly are they different? When should you use which? A bird’s eye view of their differences, a table comparing the three.

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