SQL INTERVIEW QUESTIONS AND ANSWERS FOR EXPERIENCED PDF
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SQL Interview Questions with Answers A stored procedure is a named group of SQL statements that have been previously created and stored in the server. Basic & Advanced SQL Interview Questions And Answers: This post contains Top SQL Interview Questions for Experienced as well as. Frequently asked SQL Interview Questions with detailed answers and examples. answers are given just below to them and for sql server question and answers visit "SQL server Interview Questions". .. How to store pdf file in SQL Server?.
Correlated subquery: These are queries which select the data from a table referenced in the outer query. It is not considered as an independent query as it refers to another table and refers the column in a table.
Non-Correlated subquery: This query is an independent query where the output of subquery is substituted in the main query. Define the select into statement.
Select into statement is used to directly select data from one table and insert into other, the new table gets created with same name and type as of the old table- What are ACID properties?
Answer: ACID properties refers to the four properties of transactions in SQL- Atomicity — All the operations in the transaaction are performed as a whole or not performed at all. Consistency — State of database changes only on successful committed transaction. Isolation — Even with concurrent execution of the multiple transactions, the final state of the DB would be same as if transactions got executed sequentially.
In other words each transaction is isolated from one another. This could be useful during a re-architecture or upgrade project. Normalization is the process of organizing data to avoid duplication and redundancy. Some of the advantages are:. Subquery within another subquery is called as Nested Subquery.
If the output of a subquery is depending on column values of the parent query table then the query is called Correlated Subquery.
Top SQL Interview Questions And Answers
Normalization is used to organize the data in such manner that data redundancy will never occur in the database and avoid insert, update and delete anomalies. First Normal Form 1NF: It removes all duplicate columns from the table.
Follows 1NF and creates and places data subsets in an individual table and defines relationship between tables using primary key Third Normal Form 3NF: Follows 3NF and do not define multi-valued dependencies.
In relational databases, each column should have a unique name Sequence of rows and columns in relational databases are insignificant All values are atomic and each row is unique. These triggers that contain data modification logic and find other triggers for data modification are called Nested Triggers. Collation is set of rules that check how the data is sorted by comparing it.
Such as Character data is stored using correct character sequence along with case sensitivity, type, and accent. Join keyword is used to fetch data from related two or more tables. It returns rows where there is at least one match in both the tables included in the join. Read more here. Type of joins are:. A person, place, or thing in the real world about which data can be stored in a database.
Tables store data that represents one type of entity. For example — A bank database has a customer table to store customer information. Customer table stores this information as a set of attributes columns within the table for each customer. Relation or links between entities that have something to do with each other. For example — The customer name is related to the customer account number and contact information, which might be in the same table.
There can also be relationships between separate tables for example, customer to accounts.
500 SQL Server Interview Questions and Answers - SQL FAQ PDF
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. What is the difference between Having clause and Where clause? Group functions work on the set of rows and returns one result per group. Some of the commonly used group functions are: A transaction can be defined as the sequence task that is performed on databases in a logical manner to gain certain results.
Operations performed like Creating, updating, deleting records in the database comes from transactions. In simple word, we can say that a transaction means a group of SQL queries executed on database records. It is used to set the point from where the transaction is to be rolled back.
SQL Aggregate Functions calculates values from multiple columns in a table and returns a single value. Returns number of table rows MAX: Returns largest value among the records MIN: Returns smallest value among the records SUM: Returns the first value LAST: Returns Last value.
A Stored Procedure is a collection of SQL statements that have been created and stored in the database to perform a particular task. 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.
Skip to content 1. What is Failover clustering overview? What is lock escalation? What is the difference between cross join and natural join? What is SQL Injection? For Example: List the ways in which Dynamic SQL can be executed? Following are the ways in which dynamic SQL can be executed: Write a query with parameters.
Using EXEC. What are Views used for? It is used for the following reasons: What is the difference between Union and Union All command? What are transactions in SQL?
What is the difference between clustered and non-clustered indexes?
What are the different types of locks in database? The different types of locks in database are- Shared locks — Allows data to be read-only Select operations , prevents the data to be updated when in shared lock. What is a Table in a Database? What is database testing?
What is a Relationship and what are they? There are various relationships, namely: How can you insert NULL values in a column while inserting the data? NULL values can be inserted in the following ways: What is a View in SQL? What is a join in SQL? What are the types of joins? What is field in a table? How to avoid duplicate records in a query? What is the difference between an inner and outer join?
What is SQL? Explain how to send email from SQL database? What are the different types of SQL commands? What is a temp table? A temp table is a temporary storage structure to store the data temporarily. How to make a remote connection in a database?
The following is the process to make a remote connection in database: What is the difference between delete, truncate and drop command?
Log cache is a memory pool used to read and write the log pages. A set of cache pages are available in each log cache. The synchronization is reduced between log and data buffers by managing log cache separately from the buffer cache.
You can capture and save data about each event to a file or table to analyze later. If traces are becoming too large, you can filter them based on the information you want, so that only a subset of the event data is collected. Monitoring too many events adds overhead to the server and the monitoring process and can cause the trace file or trace table to grow very large, especially when the monitoring process takes place over a long period of time.
De-normalization is used to optimize the readability and performance of the database by adding redundant data.
It covers the inefficiencies in the relational database software. De-normalization logical data design tend to improve the query responses by creating rules in the database which are called as constraints. Examples include the following:. Materialized views for implementation purpose such as: Linking attribute of one relation with other relations. To improve the performance and scalability of web applications.
A Database is defined as a structured form of data which is stored in a computer or data in an organised manner and can be accessed in various ways. It is also the collection of schemas, tables, queries, views etc. Database helps us in easily storing, accessing and manipulation of data held in a computer. The Database Management System allows a user to interact with the database.
SQL Interview Questions
SQL Online Training. It is used to fetch filtered data by searching for a particular pattern in where clause. The required query is:. What are the implications of having it OFF? If defined in inside a compound statement a local temporary table exists only for the duration of that statement but a global temporary table exists permanently in the DB but its rows disappear when the connection is closed. Views occupy no space Views are used to simply retrieve the results of complicated queries that need to be executed often.
Views are used to restrict access to the database or to hide data complexity. Triggers are special type of stored procedures that get executed when a specified event occurs. Creation of XML fragments: Ability to shred xml data to be stored in the database. Finally, storing the xml data.
It can be described in terms of:. XML Views: Creation of XML Templates: To delete existing records from a table. A NULL value is not at all same as that of zero or a blank space. NULL value represents a value which is unavailable, unknown, assigned or not applicable whereas a zero is a number and blank space is a character. Data manipulation Language or DML is used to access or manipulate data in the database.
It allows us to perform below listed functions: Insert data or rows in database Delete data from database Retrieve or fetch data Update data in database. Aggregate functions are the SQL functions which return a single value calculated from multiple values of columns.
Some of the aggregate functions in SQL are-. Count — Returns the count of the number of rows returned by the SQL expression Max — Returns the max value out of the total values Min — Returns the min value out of the total values Avg — Returns the average of the total values Sum — Returns the sum of the values returned by the SQL expression. GUI Testing deals with all the testable items that are open to the user to interaction such as Menus, Forms etc.
Database Testing deals with all the testable items that are generally hidden from the user. It validates the schema, database tables, columns, indexes, stored procedures, triggers, data duplication, orphan records, junk records. It involves in updating records in a database and verifying the same on the front end.
There is only one primary key in a table, but there can be multiple unique constrains. The primary key creates the cluster index automatically but the Unique key does not.
A subquery is a query inside another query where a query is defined to retrieve data or information back from the database. In a subquery, the outer query is called as the main query whereas the inner query is called subquery. Subqueries are always executed first and the result of the subquery is passed on to the main query.
A primary key is a column or a combination of columns which uniquely identifies a record in the database. A primary key can only have unique and not NULL values and there can be only one primary key in a table. A column is a vertical entity in a table that contains all information associated with a specific field in a table. A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and the use of more storage space to maintain the extra copy of data.
Data can be stored only in one order on disk. To support faster access according to different values, faster search like binary search for different values is desired. For this purpose, indexes are created on tables. These indexes need extra space on disk, but they allow faster search according to different frequently searched values. This article is contributed by Harsh Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.
See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. Recommended Posts:. A table can have more than one unique keys columns while there can be only one primary key. A unique key column creates non-clustered index whereas primary key creates a clustered index on the column.
Clustered indexes physically sort the rows in the table based on the clustering key by default primary key. Clustered index helps in fast retrieval of data from the databases. There can be only one clustered index in a table.If so, what are the commands? Hence, escalation is used. If Rowcount is checked after Error checking statement then it will have 0 as the value of Recordcount as it would have been reset. Truncate is a DDL command, it removes all the rows from table and also frees the space held unlike delete command.
Auto increment keyword allows the user to create a unique number to get generated whenever a new record is inserted into the table. Comment on Transactions. To replay the trace results 5. Is it possible for a stored procedure to call itself or recursive stored procedure?
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