In this example, the Email column is defined as a unique key. This constraint ensures that every email address in the Employees table is unique, but it allows one record to have a NULL email address. Key Differences between Primary Key and Unique Key Uniqueness and NULL Handling Primary Key:...
Add a Constraint to restrict a generic to numeric types Add a html content to word document in C# (row.Cells[1].Range.Text) Add a trailing back slash if one doesn't exist. Add a user to local admin group from c# Add and listen to event from static class add characters to String ad...
T-SQL GETDATE() ? ADD and SUBTRACT depending on the condition is CASE STATEMENT ADD COLUMN to variable table? Add prefix in data column Add Time in SQL HH:MM:SS to another HH:MM:SS Adding a column to a large (100 million rows) table with default constraint adding a extra column in...
index_nameindex_descriptionindex_keys PK__student__3213E83F7F60ED59clustered, unique, primary key located on PRIMARYid In the output you can see the only one index. This is the index that was automatically created because of the primary key constraint on the “id” column. ...
in performance/memory between inline constraints (on the column named check constraint) and out of...
This article will teach you the difference between a primary key and foreign key. This article will also teach you why both of these keys are important when it comes to the maintenance of a relational database structure. All the examples for this lesson are based on Microsoft SQL Server ...
the main differance is that unique key may be not null constraint or not may be.but in primary key not null constraint is defined defaultly Was this answer useful? Yes Replyrunningpumpkin Jul 7th, 2008 The main differences between a primary key and a unique key is that a primary ke...
Nevermind the inconsistency between using surrogates and natural keys throughout the model. Michael L John wrote: CreateIndexNonclustered wrote: Maybe you have an example, but I cannot think of a reason why you would need to change a primary key after a table has been c...
primary key vs unique key in SQL The primary key and unique key are two important concepts in a relational database and are used to uniquely identify a row in a table. Both primary key and unique keys can identify a row uniquely but there is some subtle difference between them which we ...
1. Difference between the private and final method in Java A private method is not visible outside the class they are declared, they are virtually final because you cannot override them. Whilefinal methodsare visible outside the class, you can call them outside the class they are declared, ...