Premium Questions for SQL Query Test
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SQL is the dominant technology for accessing application data. It is increasingly becoming a performance bottleneck when it comes to scalability. Given its dominance, SQL is a crucial skill for all engineers.
Conditional statements are a feature of most programming and query languages. They allow the programmer to control what computations are carried out based on a Boolean condition.
The SELECT statement is used to select data from a database. It is the most used SQL command.
An aggregate function is typically used in database queries to group together multiple rows to form a single value of meaningful data. A good programmer should be skilled at using data aggregation functions when interacting with databases.
Subqueries are commonly used in database interactions, making it important for a programmer to be skilled at writing them.
Knowing how to order data is a common task for every programmer.
Everyone makes mistakes. A good programmer should be able to find and fix a bug in their or someone else's code.
LEFT JOIN is one of the ways to merge rows from two tables. We use it when we also want to show rows that exist in one table, but don't exist in the other table.
The UNION operator is used to combine the result-set of two or more SELECT statements. It is often used when a report needs to be made based on multiple tables.
The GROUP BY statement groups rows by some attribute into summary rows. It is a common command when making various reports.
Even though most database insert queries are simple, a good programmer should know how to handle more complicated situations like batch inserts.
A normalized database is normally made up of multiple tables. Joins are, therefore, required to query across multiple tables.
The CASE statement is SQL's control statement. It goes through conditions and returns a value.
The performance of an application or system is important. The responsiveness and scalability of an application are all related to how performant an application is. Each algorithm and query can have a large positive or negative effect on the whole system.
RIGHT JOIN is one of the ways to merge rows from two tables. We use it when we also want to show rows that exist in one table, but don't exist in the other table.
A CTE (Common Table Expression) is a temporary result set that can be referenced within another SELECT, INSERT, UPDATE, or DELETE statement. Recursive CTEs can reference themselves, which enables developers to work with hierarchical data.
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