Set operations integrate the outcome of two entirely independent SQL queries. There are three set operations in SQL Union, Intersect, Except. These set operations are based on the principles of mathematical set theory. The set operations are applicable to the type compatible relations only, that means relations involved in operation must have an 'equal number of attributes' and … [Read more...] about Set Operations in SQL
Integrity Constraints in DBMS
Integrity constraints ensure that when the authorized users modify the database they do not disturb the data consistency. Integrity constraints are introduced while designing the database schema. The constraints are specified within the SQL DDL command like 'create table' and 'alter table' command. Let’s see, the general form of 'create table' and 'alter table' command … [Read more...] about Integrity Constraints in DBMS
Null Value in SQL
Null Value in SQL is the special value, allocated to an attribute in a relation that indicates, the information regarding the corresponding attribute is either unknown or doesn’t even exist. In this section, we will discuss the null values in detail. What is the Null Value in SQL? The null value assigned to an attribute in a relation specifies that the value for the … [Read more...] about Null Value in SQL
SQL Data Definition Language (DDL)
SQL Data Definition Language defines the set of relations in a database. SQLs DDL specifies the schema of each relation in the database and also the relevance between the relations in a database. So in this section, we will discuss SQL data definition language in detail. Content: SQL Data Definition Language Data Definition Language in SQL SQL Data Types DDL … [Read more...] about SQL Data Definition Language (DDL)
Relational Data Model
The relational data model provides conceptual tools to design the database schema of the relational database. The relational model describes the data, relationship between that data, data sematic and constraints on the data in the relational database. The relational model expresses the data and relationship among the data in the form of tables. There is a lot more to discuss … [Read more...] about Relational Data Model