Frequently Asked Sql Queries In Interview
Frequently Asked SQL Queries During Interviews
Frequently Asked Sql Queries In Interview
In SQL interviews, some commonly asked queries include selecting specific columns using the SELECT statement, filtering data using the WHERE clause, sorting data using the ORDER BY clause, joining tables using various join types like INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN, grouping data using the GROUP BY clause with aggregate functions like COUNT, SUM, AVG, etc., filtering grouped data using the HAVING clause, and utilizing subqueries to perform complex queries. Additionally, interviewers may also test candidates on their knowledge of database normalization, indexing, and performance optimization techniques to ensure a well-rounded understanding of SQL concepts.
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1 - Retrieve data from a table: One of the common SQL queries is to retrieve data from a specific table in a database. This can be achieved using the SELECT statement, specifying the columns you want to retrieve and the table from which you want to fetch the data.
2) Filter data using WHERE clause: To retrieve specific data that meets certain conditions, you can use the WHERE clause in your SELECT statement. This allows you to filter data based on criteria such as a specific value in a column or a range of values.
3) Sort data using ORDER BY: Another frequently asked query is to sort the retrieved data in a specific order. This can be done using the ORDER BY clause along with the column you want to sort by, either in ascending or descending order.
4) Join tables using JOIN: When you need to combine data from multiple tables, you can use the JOIN operation. Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN, depending on how you want to match records from the tables.
5) Group data using GROUP BY: To group data based on specific columns and perform aggregate functions such as SUM, AVG, COUNT, etc., you can use the GROUP BY clause in SQL queries.
6) Filter group data using HAVING: After grouping data using GROUP BY, if you need to apply additional filtering based on aggregate functions, you can use the HAVING clause to specify conditions for the grouped data.
7) Update data in a table: To modify existing data in a table, you can use the UPDATE statement with SET to specify the column(s) to be updated and the new values to be set based on certain conditions using the WHERE clause.
8) Insert data into a table: When you need to add new records to a table, you can use the INSERT INTO statement to specify the table and the values you want to insert into the respective columns.
9) Delete data from a table: To remove specific records from a table, you can use the DELETE FROM statement with the WHERE clause to specify the conditions for deleting the data.
10) Use subqueries: Subqueries are queries nested within another query, typically used for complex conditions, aggregate functions, or joining data from different sources. Understanding how to use subqueries is often tested in SQL interviews.
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