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SQL Interview Questions

What are the subsets of SQL?

There is three significant subset of the SQL: Data definition language (DDL):DDL is used to define the data structure it consists of the commands like CREATE, ALTER, DROP, etc. Data manipulation language (DML):DML is used to manipulate already existing data in the database. The commands in this category are SELECT, UPDATE, INSERT, etc. Data control …

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What is an inconsistent dependency?

Inconsistent dependency refers to the difficulty of accessing particular data as the path to reach the data may be missing or broken. Inconsistent dependency will leads users to search the data in the wrong table which will afterward give the error as an output.

What is Inner Join in SQL?

Inner join returns rows when there is at least one match of rows between the tables. INNER JOIN keyword joins the matching records from two tables.

Explain character-manipulation functions?

Character-manipulation functions are used to change, extract, alter the character string. One or more than one characters and words should be passed into the function, and then the function will perform its operation on those words.

What is a Data Definition Language?

Data definition language (DDL) is the subset of the database which defines the data structure of the database in the initial stage when the database is about to be created. It consists of the following commands: CREATE, ALTER and DELETE database objects such as schema, tables, view, sequence, etc.

What is Denormalization in a Database?

Denormalization is used to access the data from higher or lower normal form of database. It also processes redundancy into a table by incorporating data from the related tables. Denormalization adds required redundant term into the tables so that we can avoid using complex joins and many other complex operations. Denormalization doesn?t mean that normalization …

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Which are the different character-manipulation functions in SQL?

CONCAT: join two or more values together. SUBSTR: used to extract the string of specific length. LENGTH: return the length of the string in numerical value. INSTR: find the exact numeric position of a specified character. LPAD: padding of the left-side character value for right-justified value. RPAD: padding of right-side character value for left-justified value. …

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What is the usage of NVL() function?

The NVL() function is used to convert NULL value to the other value. NVL() function is used in Oracle it is not in SQL and MySQL server. Instead of NVL() function MySQL have IFNULL() and SQL Server have ISNULL() function.

What is a Data Manipulation Language?

Data manipulation language makes the user able to retrieve and manipulate data. It is used to perform the following operations. Insert data into database through INSERT command. Retrieve data from the database through SELECT command. Update data in the database through UPDATE command. Delete data from the database through DELETE command.

What are the types of operators available in SQL?

Operators are the special keywords or special characters reserved for performing particular operations and are used in the SQL queries. There is three type of operators used in SQL: Arithmetic operators: addition (+), subtraction (-), multiplication (*), division (/), etc. Logical operators: ALL, AND, ANY, ISNULL, EXISTS, BETWEEN, IN, LIKE, NOT, OR, UNIQUE. Comparison operator: …

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