Legasis Services Interview Questions and Answers

Joins in SQL are used to combine data from two or more tables based on a related column.

• Joins are used to retrieve data from multiple tables in a single query.

• There are different types of joins such as inner join, left join, right join, and full outer join.

• The join condition is specified using the ON keyword and the related columns.

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column;

A group by clause is used in SQL to group rows with the same values into summary rows.

• It is used with the SELECT statement.

• It is followed by one or more columns to group the result set by.

• It is often used with aggregate functions like COUNT, SUM, AVG, etc.

• It can be used to generate summary reports.

• Example: SELECT column1, COUNT(column2) FROM table_name GROUP BY column1;

SQL joins are used to combine data from two or more tables based on a related column between them.

• Inner Join: returns only the matching rows from both tables

• Left Join: returns all the rows from the left table and matching rows from the right table

• Right Join: returns all the rows from the right table and matching rows from the left table

• Full Outer Join: returns all the rows from both tables, with NULL values in the colu...read more

DDL and DML are SQL commands used to manipulate databases. DDL is used to create, modify, and delete database objects, while DML is used to manipulate data within those objects.

• DDL stands for Data Definition Language and includes commands like CREATE, ALTER, and DROP.

• DDL commands are used to create, modify, and delete database objects like tables, indexes, and views.

• DML stands for Data Manipulation Language and include...read more