Sql Technical Interview Questions And Answers Pdf
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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.
- Top 65 SQL Interview Questions You Must Prepare In 2021
- 100+ Most Popular SQL Interview Questions And Answers
- SQL Interview Questions asked in Top Companies in 2021
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.
Top 65 SQL Interview Questions You Must Prepare In 2021
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. What is lock escalation? This increases system performance as each lock is nothing but a memory structure. Too many locks would mean more consumption of memory. Hence, escalation is used. Lock escalation from SQL Server 7. It is the process of converting a lot of low-level locks into higher-level locks. It should be disabled immediately thereafter. For any disaster recovery, the account will be automatically enabled.
It should not be used for normal operations. What is the difference between cross join and natural join? Answer: The cross join produces the cross product or Cartesian product of two tables whereas the natural join is based on all the columns having the same name and data types in both the tables. What is SQL Injection? Answer: SQL Injection is a type of database attack technique where malicious SQL statements are inserted into an entry field of database such that once it is executed the database is opened for an attacker.
This technique is usually used for attacking Data-Driven Applications to have access to sensitive data and perform administrative tasks on databases. List the ways in which Dynamic SQL can be executed?
Answer: Following are the ways in which dynamic SQL can be executed:. Write a query with parameters. Using EXEC. What are Views used for? Answer: A view refers to a logical snapshot based on a table or another view. It is used for the following reasons:. Answer: Autoincrement keyword allows the user to create a unique number to get generated whenever a new record is inserted into the table.
What is the difference between Union and Union All command? Answer: The fundamental difference between Union and Union All command is, Union is by default distinct i. Whereas, Union All combines all the rows including duplicates in the result set of different select statements. What are transactions in SQL? Answer: The transaction is a set of operations performed in a logical sequence.
It is executed as a whole, if any statement in the transaction fails, the whole transaction is marked as failed and not committed to the database. There are 3 types of SQL sandbox, such as. What is the difference between clustered and non-clustered indexes? Answer: One table can have only one clustered index but multiple nonclustered indexes. Clustered indexes can be read rapidly rather than non-clustered indexes. Clustered indexes store data physically in the table or view and non-clustered indexes do not store data in the table as it has separate structure from the data row.
What are the different types of locks in the database? Answer: The different types of locks in the database are-. What is a Table in a Database? Answer: A table is a database object used to store records in a field in the form of columns and rows that holds data. What is database testing? Answer: Database testing involves checking the integrity of actual data in the front end with the data present in the database.
What is a Relationship and what are they? Answer: Relation or links are between entities that have something to do with each other.
Relationships are defined as the connection between the tables in a database. How can you insert NULL values in a column while inserting the data? Answer: NULL values can be inserted in the following ways:. Implicitly by omitting column from column list. What is a View in SQL? Answer: Views in SQL are kind of virtual tables. A view also has rows and columns as they are in a real table in the database. We can create a view by selecting fields from one or more tables present in the database.
A View can either have all the rows of a table or specific rows based on a certain condition. What is a join in SQL? What are the types of joins? Answer: An SQL Join statement is used to combine data or rows from two or more tables based on a common field between them. This keyword will create the result-set by combining all rows from both the tables where the condition satisfies i.
The rows for which there is no matching row on the right side, the result-set will contain null. This join returns all the rows of the table on the right side of the join and matching rows for the table on the left side of the join. The rows for which there is no matching row on the left side, the result-set will contain null. The result-set will contain all the rows from both the tables.
The rows for which there is no matching, the result-set will contain NULL values. To know about each of these joins in details, refer this. The use of indexes and constraints helps in faster retrieval and better management of data within the databases.
Whereas in DBMS there is no relation between the tables data may even be stored in files. RDBMS has primary keys and data is stored in tables. DBMS has no concept of primary keys with data stored in navigational or hierarchical form.
What is a field in a table? Answer: A field is an entity used for storing a particular type of data within a table like numbers, characters, dates, etc. How to avoid duplicate records in a query?
It eliminates all the duplicated values. View Detailed Post. What is the difference between an inner and outer join? Answer: An inner join returns rows when there is at least some matching data between two or more tables that are being compared.
An outer join returns rows from both tables that include the records that are unmatched from one or both the tables. What is SQL? It is a language used to interact with the database, i. Using SQL, we can do many things, for example — we can execute queries, we can insert records in a table, we can update records, we can create a database, we can create a table, we can delete a table, etc. Explain how to send email from SQL database?
Answer: SQL Server has a feature for sending mails. Stored procedures can also be used for sending mail on demand. The following is the process for sending emails from the database.
Write a script to send an e-mail. The following is the script. What are the different types of SQL commands? Answer: SQL commands are the set of commands used to communicate and manage the data present in the database. The different type of SQL commands are-.
What is the temp table? Answer: A temp table is a temporary storage structure to store the data temporarily. How to make a remote connection in a database?
Answer: The following is the process to make a remote connection in the database:. What is the difference between delete, truncate and drop command? Answer: The difference between the Delete, Truncate and Drop command is — Delete command is a DML command, it removes rows from a table based on the condition specified in the where clause, being a DML statement we can rollback changes made by delete command.
Truncate is a DDL command, it removes all the rows from a table and also frees the space held, unlike delete command. It takes a lock on the table while delete command takes a lock on rows of the table.
100+ Most Popular SQL Interview Questions And Answers
There is given sql interview questions and answers that has been asked in many companies. SQL is a standard query language used for maintaining the relational database and perform many different operations of data manipulation on the data. SQL initially was invented in It is a database language used for database creation, deletion, fetching rows and modifying rows, etc. It appeared in SQL is one of the often used languages for maintaining the relational database.
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.
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Following is a curated list of SQL interview questions and answers, which are likely to be SQL Interview Questions PDF file: Download here.
SQL Interview Questions asked in Top Companies in 2021
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