Sql Technical Interview Questions And Answers Pdf

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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. In order to get a job, candidates need to crack the interview in which they are asked various SQL interview questions. Following is a curated list of SQL interview questions and answers, which are likely to be asked during the SQL interview. Candidates are likely to be asked basic SQL interview questions to advance level SQL questions depending on their experience and various other factors.

Advanced SQL Interview Questions And Answers Pdf

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. Data warehouse refers to a central repository of data from multiple sources of information.

Those data are consolidated, transformed and made available for the mining as well as online processing. A table is a database object used to store records in a field in the form of columns and rows that holds data.

A column is a vertical entity in a table that contains all information associated with a specific field in a table. Database Management System is a collection of programs that enables a user to store, retrieve, update and delete information from a database. There are two types of DBMS 1. Non-Relational Database Management System. DCL commands are used to create roles, grant permission, and control access to the database objects. An index is used to speed up the performance of queries.

It makes faster retrieval of data from the table. The index can be created on one column or a group of columns. Unique Index: Unique Indexes helps maintain data integrity by ensuring that no two rows of data in a table have identical key values. A unique index can be applied automatically when a primary key is defined.

It ensures that the values in the index key columns are unique. Clustered Index: Clustered Index reorders the physical order of the table and search based on the key values. There will be only one clustered index per table. Each table can have many non-clustered indexes. The difference between the clustered and non-clustered index in SQL is as follows: Clustered Index: It is used for easy retrieval of data from the database and it is faster.

One table can only have one clustered index It alters the way records are stored in a database as it sorts out rows by the column which is set to be clustered index. Non-Clustered Index: It is slower compared to the Clustered index. A view is like a subset of a table which is stored logically in a database.

A view is a virtual table. It contains rows and columns similar to a real table. The fields in the view are fields from one or more real tables. Views do not contain data of their own. They are used to restrict access to the database or to hide data complexity. What are the advantages of Views? Some of the advantages of Views are. Database Relationship is defined as the connection between the tables in a database. There are various database relationships namely. One to One Relationship 2.

One to Many Relationship 3. Many to One Relationship 4. Self-Referencing Relationship. A database query is a request for data or information from a database table or combination of tables. A database query can be either a select query or an action query. A Subquery is a SQL query within another query.

It is a subset of a Select statement whose return values are used in filtering the conditions of the main query. Correlated: In a SQL database query, a correlated subquery is a subquery that uses values from the outer query in order to complete. Because a correlated subquery requires the outer query to be executed first, the correlated subquery must run once for every row in the outer query.

It is also known as a synchronized subquery. Non-Correlated: A Non-correlated subquery is a subquery in which both outer query and inner query are independent to each other. Local Variables: Local variables can be used or exist only inside the function. These variables are not used or referred by any other functions. These are not known to other functions. Variables can be created whenever that function is called. Global Variables: Global variables can be used or exist throughout the program.

Same variable declared in global cannot be used in functions. Global variables cannot be created whenever that function is called. Data integrity defines the accuracy and consistency of the data stored in a database.

It also defines integrity constraints to enforce business rules on the data when it is entered into an application or a database. Auto increment keyword allows the user to create a unique number to get generated when a new record is inserted into a table. Auto increment keyword can be used whenever Primary Key is used. It eliminates all the duplicated values. Inner Join: An inner join returns rows when there is at least some matching data between two or more tables that are being compared.

Outer Join: An outer join returns rows from both tables that include the records that are unmatched from one or both the tables. SQL constraints are the set of rules that enforced some restriction while inserting, deleting or updating of data in the databases.

A field with a NULL value is a field with no value. A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left blank during record creation. Assume, there is a field in a table is optional and it is possible to insert a record without adding a value to the optional field then the field will be saved with a NULL value.

As I mentioned earlier, Null value is field with no value which is different from zero value and blank space. Null value is a field with no value. Zero is a number Blank space is the value we provide. Denormalization is a database optimization technique used to increase the performance of a database infrastructure.

It involves in the process of adding redundant data to one or more tables. In a normalized database, we store data in separate logical tables and attempt to minimize redundant data.

The stored procedure accepts input parameters and processes them and returns a single value such as a number or text value or a result set set of rows. We need to decide what type of data to store inside each and every column of a table while creating a SQL table. The largest number that can be represented in a single byte is or The number of possible values is i. These guarantees that the database transactions are processed reliably. The new table will be created with the column-names and types as defined in the old table.

You can create new column names using the AS clause. What is the difference between Delete, Truncate and Drop command? Interviewer may ask you this question in another way as what are the advantages of Union All over Union. Both Union and Union All concatenate the result of two tables but the way these two queries handle duplicates are different. Union query checks the duplicate values which consumes some time to remove the duplicate records. Last record from both the tables are same.

Where clause cannot be used with Aggregate functions, but the Having clause can. SQL aggregate functions return a single value, calculated from values in a column. Some of the aggregate functions in SQL are as follows. View Detailed Post. SQL string functions are used primarily for string manipulation.

Some of the widely used SQL string functions are. As the name suggests these are written by users as per their requirement. User-defined functions are the functions written to use a logic whenever required. Scalar functions return unit, variant defined the return clause. Inline Table-valued functions and Multi-statement valued functions return table as a return.

A self-join is a join in which a table is joined with itself, especially when the table has a Foreign Key which references its own Primary Key. Cross join produces a result set which is the number of rows in the first table multiplied by a number of rows in the second table if no WHERE clause is used along with Cross join.

This kind of result is known as Cartesian Product. If suppose, Where clause is used in cross join then the query will work like an Inner join.

Collation is defined as a set of rules that determine how character data can be sorted as well as compared. Character data is sorted using rules that define the correct character sequence along with options for specifying case-sensitivity, character width, accent marks, kana character types.

Different types of collation sensitivity are as follows Case Sensitivity: A and a and B and b. Kana Sensitivity: Japanese Kana characters.


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

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.

100+ Most Popular SQL Interview Questions And Answers

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Top 65 SQL Interview Questions You Must Prepare In 2021

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. Data warehouse refers to a central repository of data from multiple sources of information.

There are a lot of opportunities from many reputed companies in the world. According to research SQL by Microsoft grew at In the upcoming era, the competition will be more heated than is has been for years.

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.


  1. Marc M. 18.05.2021 at 20:13

    Following is a curated list of SQL interview questions and answers, which are likely to be SQL Interview Questions PDF file: Download here.