Question

Define a SQL join and name different types of joins.

a) A join is a combination of two or more tables to retrieve data. Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.
b) A join is a data manipulation command. Types of joins include SELECT, INSERT, and DELETE.
c) A join is a data definition command. Types of joins include CREATE, ALTER, and DROP.
d) A join is a constraint in SQL. Types of joins include PRIMARY KEY, FOREIGN KEY, and CHECK.

Answer 1

A SQL join is a clause used in SQL to combine rows from two or more tables, based on a related column between them. Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN. The correct answer to the question is option a).

Step-by-step explanation:

A SQL join is a clause used in Structured Query Language (SQL) to combine rows from two or more tables, based on a related column between them. There are several different types of SQL joins, which allow for the retrieval of data from multiple tables in a relational database.

The primary types of joins are:

• INNER JOIN: Selects records that have matching values in both tables.
• LEFT JOIN (or LEFT OUTER JOIN): Selects all records from the left table, and the matched records from the right table. If there is no match, the result is NULL on the side of the right table.
• RIGHT JOIN (or RIGHT OUTER JOIN): Selects all records from the right table, and the matched records from the left table. If there is no match, the result is NULL on the side of the left table.
• FULL JOIN (or FULL OUTER JOIN): Selects all records when there is a match in either left or right table. When there is no match, the result is NULL from the table that does not have a match.

For clarity, option a) in your question is the correct definition of a SQL join and includes the various types of joins available in SQL.