pdf of sql interview questions and answers

Pdf of sql interview questions and answers

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Practice SQL Questions asked in Interviews

A database is a collection of information in an organized form for faster and better access, storage, and manipulation. It can also be defined as a collection of tables, schema, views, and other database objects.

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Now the client wants to insert a record after the identity value 7 with its identity value starting from Write a single query to calculate the sum of all positive values of x and he sum of all negative values of x. Although there are 4 customers not referred by Jane Smith including Jane Smith herself , the query will only return one: Pat Richards.

This will return the same faulty set as the original. Those particular operators will always evaluate to true or false. Given a table TBL with a field Nmbr that has rows with the following values:. Write a single SQL statement to concatenate all the customer names into the following single semicolon-separated string:.

This is close, but will have an undesired trailing ;. One way of fixing that could be:. This will give the third-highest salary from the Employee table.

Considering the database schema displayed in the SQLServer-style diagram below, write a SQL query to return a list of all the invoices. The list should be ordered by billing date. There is nothing tricky in this one, it just covers the basics:. If not, any invoices by customers not referred by somebody will be left out altogether. Did the candidate alias the tables in the JOIN? Most experienced T-SQL programmers always do this, because repeating the full table name each time it needs to be referenced gets tedious quickly.

Again, this is something most experienced programmers do automatically, whether or not there would be a conflict. And again, in this case there would be a conflict, so the query would break if the candidate neglected to do so. Note that this query will not return Invoices that do not have an associated Customer. This may be the correct behavior for most cases e. UNION merges the contents of two structurally-compatible tables into a single combined table.

So, in cases where is is certain that there will not be any duplicates, or where having duplicates is not a problem, use of UNION ALL would be recommended for performance reasons. This is the default type of join if no specific JOIN type is specified. Explain your answer and also provide an alternative version of this query that will avoid the issue that it exposes. Surprisingly, given the sample data provided, the result of this query will be an empty set.

It will always be true since ID is not a member of dbo. As such, it will refer to the envelope table comparing itself to itself! If there are 10 records in the Emp table and 5 records in the Dept table, how many rows will be displayed in the result of the following SQL query:.

In Oracle, the minus keyword is used instead. MySQL does not support the except function. Write a SQL query to find the 10th highest employee salary from an Employee table.

Explain your answer. However, those salaries will be listed in descending order. That was necessary for the first query to work, but now picking the top 1 from that list will give you the highest salary not the the 10th highest salary. Therefore, the second query reorders the 10 records in ascending order which the default sort order and then selects the top record which will now be the lowest of those 10 salaries.

Not all databases support the TOP keyword. Why might you want to do this? The key is the AND a! Write a query to to get the list of users who took the a training lesson more than once in the same day, grouped by user and training lesson, each ordered from the most recent lesson date to oldest date.

Execution plans are very useful for helping a developer understand and analyze the performance characteristics of a query or stored procedure, since the plan is used to execute the query or stored procedure. If this option is turned on, it will display query execution plans in a separate window when a query is run. List and explain each of the ACID properties that collectively guarantee that database transactions are processed reliably.

ACID Atomicity, Consistency, Isolation, Durability is a set of properties that guarantee that database transactions are processed reliably. They are defined as follows:. Given a table dbo. With the NVL exp1, exp2 function, if exp1 is not null, then the value of exp1 is returned; otherwise, the value of exp2 is returned, but case to the same data type as that of exp1. With the NVL2 exp1, exp2, exp3 function, if exp1 is not null, then exp2 is returned; otherwise, the value of exp3 is returned.

Provide an example. Imagine a single column in a table that is populated with either a single digit or a single character a-z, A-Z. When stored in a database, varchar2 uses only the allocated space. But when stored in a database, char always uses the maximum length and is blank-padded.

There is more to interviewing than tricky technical questions, so these are intended merely as a guide. As an SQL developer, Jonas has automated financial reporting for a national bank and built a data quality framework along with multiple dashboards, and as a data scientist, he's analyzed customer behavior and financial transactions using machine learning. Matthew has over 15 years of experience in database management and software development, with a strong focus on full-stack web applications.

He specializes in Django and Vue. He also works with relational databases and large datasets. He builds high quality and high-performance back-end systems and creates web applications with good UX using modern frameworks like Angular or React.

He's proactive and results-oriented with a love of not only writing, but also removing code to ensure efficient, stable, and flexible software is delivered within the projected scope and budget.

Looking for SQL Developers experts? Submit an Interview Question. If so, how? If not, why not? What would be a better way to write it? Id, i. BillingDate, c. Name, r. View answer. Note: You may assume that there are at least 10 records in the Employee table. What is an execution plan? When would you use it?

How would you view the execution plan? They are defined as follows: Atomicity. An atomic system must guarantee atomicity in each and every situation, including power failures, errors, and crashes. The consistency property ensures that any transaction will bring the database from one valid state to another.

Any data written to the database must be valid according to all defined rules, including constraints, cascades, triggers, and any combination thereof. The isolation property ensures that the concurrent execution of transactions results in a system state that would be obtained if transactions were executed serially, i. Providing isolation is the main goal of concurrency control.

Depending on concurrency control method i. Durability means that once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors. In a relational database, for instance, once a group of SQL statements execute, the results need to be stored permanently even if the database crashes immediately thereafter.

To defend against power loss, transactions or their effects must be recorded in a non-volatile memory. How do they differ? How can you select all the even number records from a table? All the odd number records?

The filtering occurs before any groupings are made. What will be the output of the below query, given an Employee table having 10 records? What is the difference between single-row functions and multiple-row functions? What is the group by clause used for? Single-row functions work with single row at a time. Multiple-row functions work with data of multiple rows at a time.

The group by clause combines all those records that have identical values in a particular field or any group of fields. What is the difference between char and varchar2? Can we insert a row for identity column implicitly? How do you get the last id without the max function? Suppose in a table, seven records are there. The column is an identity column. Is it possible? How can you use a CTE to return the fifth highest or Nth highest salary from a table?

Given the following table named A : x 2 -2 4 -4 -3 0 2 Write a single query to calculate the sum of all positive values of x and he sum of all negative values of x.

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What is Failover clustering overview? Answer: Failover clustering is mainly used for data availability. Typically, in a failover cluster, there are two machines. One machine provides the basic services and the second is available to run the service when the primary system fails. The primary system is monitored periodically to check if it works. This monitoring may be performed by the failover computer or an independent system also called a cluster controller. In an event of failure of the primary computer, the failover system takes control.

In this article, we have covered 90+ most popular SQL interview questions with answers. These are useful questions for freshers and.

Practice SQL Questions asked in Interviews

Now the client wants to insert a record after the identity value 7 with its identity value starting from Write a single query to calculate the sum of all positive values of x and he sum of all negative values of x. Although there are 4 customers not referred by Jane Smith including Jane Smith herself , the query will only return one: Pat Richards.

Home page Contact Us. Net DWH New. Define SQL?

A database is an organized collection of data, stored and retrieved digitally from a remote or local computer system. Databases can be vast and complex, and such databases are developed using fixed design and modeling approaches. DBMS is a system software responsible for the creation, retrieval, updation and management of the database. It ensures that our data is consistent, organized and is easily accessible by serving as an interface between the database and its end users or application softwares. The key difference here, compared to DBMS, is that RDBMS stores data in the form of a collection of tables and relations can be defined between the common fields of these tables.

SQL Interview Questions

What is BCP?


  • Destlegdtetic1975 16.04.2021 at 15:47

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  • Melissa S. 20.04.2021 at 13:54

    SQL programming skills are highly desirable and required in the market, as there is a massive use of Database Management Systems DBMS in almost every software application.

  • Julien L. 21.04.2021 at 00:10

    SQL is one of the most widely used languages.

  • Esmirna G. 23.04.2021 at 09:55

    Frequently Asked SQL Interview Questions and Answers for Freshers and Experienced. 1. What is DBMS? A Database Management System .


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