Technical Interview Questions
Primary key and unique key both are the essential constraints of the SQL, but there is a small difference between them Primary key carries unique value but the field of the primary key cannot be Null on the other hand unique key also carry unique value but it can have a single Null value field. … Read more
Unique key constraint uniquely identifies each record in the database. This key provides uniqueness for the column or set of columns. The Unique key cannot accept a duplicate value. The unique key can accept only on Null value. A unique key in SQL is a set of one or more columns in a table that … Read more
A foreign key is specified as a key which is related to the primary key of another table. A relationship needs to be created between two tables by referencing foreign key with the primary key of another table. Foreign key acts like a cross-reference between tables as it refers to the primary key of other … Read more
A primary key is a field or the combination of fields which uniquely specify a row. The Primary key is a special kind of unique key. Primary key values cannot be NULL. For example, the Social Security Number can be treated as the primary key for any individual. A primary key in SQL is a … Read more
A table is a set of organized data. It has rows and columns. Rows here refers to the tuples which represent the simple data item and columns are the attribute of the data items present in particular row. Columns can categorize as vertical, and Rows are horizontal. A table contains a specified number of the … Read more