Constraints

Ranga Babu
Data check

SQL Foreign key

April 5, 2019 by

In this article let us review different ways to create a SQL foreign key, rules on updates and deletes, enabling foreign key constraints, disabling foreign key constraints and not for replication in foreign keys.

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Bojan Petrovic

SQL index overview and strategy

November 27, 2018 by

A SQL index is used to retrieve data from a database very fast. Indexing a table or view is, without a doubt, one of the best ways to improve the performance of queries and applications.

A SQL index is a quick lookup table for finding records users need to search frequently. An index is small, fast, and optimized for quick lookups. It is very useful for connecting the relational tables and searching large tables.

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Ahmad Yaseen

Constraints in SQL Server: SQL NOT NULL, UNIQUE and SQL PRIMARY KEY

October 25, 2017 by

This article explains the SQL NOT NULL, Unique and SQL Primary Key constraints in SQL Server with examples.

Constraints in SQL Server are predefined rules and restrictions that are enforced in a single column or multiple columns, regarding the values allowed in the columns, to maintain the integrity, accuracy, and reliability of that column’s data. In other words, if the inserted data meets the constraint rule, it will be inserted successfully. If the inserted data violates the defined constraint, the insert operation will be aborted.

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