by Dexter | Jan 5, 2021 | Oracle SQL
A Foreign Key constraint establishes a link or relationship between columns in one table with column( WHICH IS A PRIMARY KEY) from other table. A Foreign key constraint enforces referential integrity between two tables, one which is termed as child table in which we...
by Dexter | Jan 5, 2021 | Oracle SQL
When we apply UNIQUE constraint to a column(s) in table, Oracle ensures that each row within that column(s) is unique. However, NULL values are allowed for multiple rows as long as the combination is unique as well. One of the difference between Primary key and Unique...
by Dexter | Jan 5, 2021 | Oracle SQL
In this article, we will be learning about the Primary constraints and how to create, alter, drop or enable/disable them in Oracle. What is a Primary Key? The Primary Key constraint is used for uniquely identifying each row of a table. Primary constraint can be...
by Dexter | Jan 5, 2021 | Oracle SQL
The literal meaning of constraints in English dictionary is Limitation or Restriction and that’s the exact role that Constraints play in Oracle. Constraints are added to columns in table definitions to specify rules that prevent invalid data from entering into...
by Dexter | Jan 5, 2021 | Oracle SQL
ALTER TABLE ADD statement is used to add one or more than one columns to a table in Oracle database. Syntax: The syntax of Oracle ALTER TABLE ADD statement is as follows: ALTER TABLE table_name ADD column_name data_type constraint; Here, table_name – It is the...
by Dexter | Jan 5, 2021 | Oracle SQL
ALTER TABLE MODIFY statement is used for modifying the attributes or changing the definition of existing columns in Oracle database. Syntax: The syntax of Oracle ALTER TABLE MODIFY statement is as follows: ALTER TABLE table_name MODIFY column_name modificiation; Here,...
