If you want to perform well at the SQL job interview, these are the concepts you need to know:
- Data Definition Language (DDL) keywords.
- Data Manipulation Language (DML) keywords.
- Data Control Language (DCL) keywords.
- Transaction Control Language (TCL) keywords.
- SQL constraints.
- JOINs.
- indexes.
- transactions.
Indeed, What are the basic SQL interview questions?
SQL Interview Questions
- What is the difference between SQL and MySQL?
- What are the different subsets of SQL?
- What do you mean by DBMS? …
- What do you mean by table and field in SQL?
- What are joins in SQL?
- What is the difference between CHAR and VARCHAR2 datatype in SQL?
- What is the Primary key?
- What are Constraints?
Then, Is SQL technical skill? SQL: The one technical skill all non-technicals need to know.
What are the 5 basic SQL commands? There are five types of SQL commands: DDL, DML, DCL, TCL, and DQL.
- Data Definition Language (DDL) DDL changes the structure of the table like creating a table, deleting a table, altering a table, etc. …
- Data Manipulation Language. …
- Data Control Language. …
- Transaction Control Language. …
- Data Query Language.
In the same way What is a unique key in SQL? The UNIQUE constraint ensures that all values in a column are different. Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint.
What are SQL constraints?
SQL constraints are used to specify rules for the data in a table. Constraints are used to limit the type of data that can go into a table. This ensures the accuracy and reliability of the data in the table. If there is any violation between the constraint and the data action, the action is aborted.
What are SQL indexes?
An index contains keys built from one or more columns in the table or view. These keys are stored in a structure (B-tree) that enables SQL Server to find the row or rows associated with the key values quickly and efficiently. SQL Server documentation uses the term B-tree generally in reference to indexes.
What is not null in SQL?
The NOT NULL constraint enforces a column to not accept NULL values, which means that you cannot insert or update a record without adding a value to this field.
What is normalization in SQL?
“Database normalization is the process of restructuring a relational database in accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity.
What is cursor in SQL?
A cursor in SQL is a temporary work area created in system memory when a SQL statement is executed. A SQL cursor is a set of rows together with a pointer that identifies a current row. It is a database object to retrieve data from a result set one row at a time.
What are 5 types of constraints?
Types of Constraints in DBMS-
- Domain constraint.
- Tuple Uniqueness constraint.
- Key constraint.
- Entity Integrity constraint.
- Referential Integrity constraint.
What is SQL optimization?
SQL Query optimization is defined as the iterative process of enhancing the performance of a query in terms of execution time, the number of disk accesses, and many more cost measuring criteria. Data is an integral part of any application.
What are the types of JOINs in SQL?
Different Types of SQL JOINs
- (INNER) JOIN : Returns records that have matching values in both tables.
- LEFT (OUTER) JOIN : Returns all records from the left table, and the matched records from the right table.
- RIGHT (OUTER) JOIN : Returns all records from the right table, and the matched records from the left table.
How delete a column in SQL?
Right-click the column you want to delete and choose Delete Column from the shortcut menu. If the column participates in a relationship (FOREIGN KEY or PRIMARY KEY), a message prompts you to confirm the deletion of the selected columns and their relationships. Choose Yes.
What is left join SQL?
The LEFT JOIN command returns all rows from the left table, and the matching rows from the right table. The result is NULL from the right side, if there is no match.
What is trigger in SQL?
A trigger is a special type of stored procedure that automatically runs when an event occurs in the database server. DML triggers run when a user tries to modify data through a data manipulation language (DML) event. DML events are INSERT, UPDATE, or DELETE statements on a table or view.
What is 1NF 2NF and 3NF?
A relation is in 1NF if it contains an atomic value. 2NF. A relation will be in 2NF if it is in 1NF and all non-key attributes are fully functional dependent on the primary key. 3NF. A relation will be in 3NF if it is in 2NF and no transition dependency exists.
Why is 2NF used?
A table is in 2NF, only if a relation is in 1NF and meet all the rules, and every non-key attribute is fully dependent on primary key. The Second Normal Form eliminates partial dependencies on primary keys.
What are SQL views?
In SQL, a view is a virtual table based on the result-set of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.
What is temp table in SQL?
What is a temp table? As its name indicates, temporary tables are used to store data temporarily and they can perform CRUD (Create, Read, Update, and Delete), join, and some other operations like the persistent database tables.
What is execute in SQL?
The EXEC command is used to execute a stored procedure, or a SQL string passed to it. You can also use full command EXECUTE which is the same as EXEC.
What is sequence in SQL?
A sequence is a user-defined schema bound object that generates a sequence of numeric values according to the specification with which the sequence was created. The sequence of numeric values is generated in an ascending or descending order at a defined interval and can be configured to restart (cycle) when exhausted.
What is key DBMS?
A key in DBMS is an attribute or a set of attributes that help to uniquely identify a tuple (or row) in a relation (or table). Keys are also used to establish relationships between the different tables and columns of a relational database. Individual values in a key are called key values.
What is join in DBMS?
In DBMS, a join statement is mainly used to combine two tables based on a specified common field between them. If we talk in terms of Relational algebra, it is the cartesian product of two tables followed by the selection operation.
What is tuple in DBMS?
(1) In a relational database, a tuple is one record (one row). See record and relational database. (2) A set of values passed from one programming language to another application program or to a system program such as the operating system.
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