Write a note on relational model.

The relational model in DBMS is an abstract model used to organize and manage the data stored in a database. It stores data in two-dimensional inter-related tables, also known as relations in which each row represents an entity and each column represents the properties of the entity.

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Exaplain with example how ER diagram is converted into tables.

Step 1 − Conversion of strong entities For each strong entity create a separate table with the same name. Includes all attributes, if there is any composite attribute divided into simple attributes and has to be included. Ignore multivalued attributes at this stage. Select the p key for the table. Step 2 − Conversion of weak entity For each weak entity create a separate table with the same name. Include all attributes. Include the P key of a strong entity as foreign key is the weak entity. Declare the combination of foreign key and decimator attribute as P key from the weak entity. Step 3 − Conversion of one-to-one relationship For each one to one relation, say A and B modify either A side or B side to include the P key of the other side as a foreign key. If A or B is having total participation, then that should be a modified table. If a relationship consists of attributes, include them also in the modified table. Step 4 − Conversion of one-to-many relationship For each one to many rel...
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Explain any five relational algebra operators.

SELECT (σ): The SELECT operation is used for selecting a subset of the tuples according to a given selection condition. Sigma(σ)Symbol denotes it. It is used as an expression to choose tuples which meet the selection condition. Select operator selects tuples that satisfy a given predicate. Projection(π) The projection eliminates all attributes of the input relation but those mentioned in the projection list. The projection method defines a relation that contains a vertical subset of Relation. This helps to extract the values of specified attributes to eliminates duplicate values. (pi) symbol is used to choose attributes from a relation. This operator helps you to keep specific columns from a relation and discards the other columns. Rename (ρ) Rename is a unary operation used for renaming attributes of a relation. ρ (a/b)R will rename the attribute ‘b’ of relation by ‘a’. Union operation (υ) UNION is symbolized by ∪ symbol. It includes all tuples that are in tables A or in B. It also el...
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. What is join? Explain the types of join with example.

A JOIN clause is used to combine rows from two or more tables, based on a related column between them Different Types of SQL JOINs Here are the different types of the JOINs in SQL: (INNER) JOIN: Returns records that have matching values in both tables LEFT (OUTER) JOIN: Returns all records from the left table, and the matched records from the right table RIGHT (OUTER) JOIN: Returns all records from the right table, and the matched records from the left table FULL (OUTER) JOIN: Returns all records when there is a match in either left or right table
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