Data retrieval from data base is done through appropriate and efficient use of SQL. Three concepts from relational theory encompass the capability of the SELECT statement: projection, selection, and joining. Projection: A project operation selects only certain columns (fields) from a table.
What are the capabilities of SQL?
SQL Server offers a high level of security, reliability and scalability depending on the business needs. The server offers a wide data storage, full text query search, buffer management, logging and transaction, fast data retrieval etc. it offers a variety of replication services to avoid loosing data.
What are the three basic parts of an SQL statement?
SQL has three main components: the Data Manipulation Language (DML), the Data Definition Language (DDL), and the Data Control Language (DCL).
What are the capabilities of a SELECT statement?
A SELECT statement retrieves data from database. With a SELECT statement, you can use the following capabilities: Projection: select the columns in a table that are returned by a query. Selection: select the rows in a table that are returned by a query using certain criteria to restrict the result.
What are the elements of a SQL statement?
SQL Language Elements
- Keywords. Each SQL statement contains one or more keywords.
- Identifiers. Identifiers are names of objects in the database, such as user IDs, tables, and columns.
- Strings. …
- Expressions. …
- Search Conditions. …
- Special Values. …
- Variables. …
What is the three level architecture of a database system?
The three levels present in this architecture are Physical level, Conceptual level and External level.
What is SQL and important features of SQL?
SQL is used to define the data in the database and manipulate it when needed. SQL is used to create and drop the database and table. SQL is used to create a view, stored procedure, function in a database. SQL allows users to set permissions on tables, procedures, and views.
What are the types of SQL statements?
Types of SQL Statements
- Data Definition Language (DDL) Statements.
- Data Manipulation Language (DML) Statements.
- Transaction Control Statements.
- Session Control Statements.
- System Control Statement.
- Embedded SQL Statements.
What does in SQL statement mean?
Description. The SQL IN condition (sometimes called the IN operator) allows you to easily test if an expression matches any value in a list of values. It is used to help reduce the need for multiple OR conditions in a SELECT, INSERT, UPDATE, or DELETE statement.
What is the basic structure of SQL?
SQL includes Data Definition Language (DDL) statements and Data Manipulation Language (DML) statements. DDL statements, such as CREATE, ALTER, and DROP, modify the schema of a database. DML statements, such as SELECT, INSERT, UPDATE, and DELETE, manipulate data in tables.
What are aggregate function in SQL?
An aggregate function in SQL performs a calculation on multiple values and returns a single value. SQL provides many aggregate functions that include avg, count, sum, min, max, etc. An aggregate function ignores NULL values when it performs the calculation, except for the count function.
Which statement about SQL is true?
The correct answer is, option (a): Null values are displayed last in the ascending sequences. And rest all are incorrect answers pertaining to SQL.
What are the three primary elements of a SELECT statement?
The remainder of this subsection examines the 3 major clauses of the SELECT statement, detailing their syntax and semantics: SELECT Clause — specifies the table columns retrieved. FROM Clause — specifies the tables to be accessed. WHERE Clause — specifies which rows in the FROM tables to use.
What is choose function in SQL?
SQL Server CHOOSE() function overview
The CHOOSE() function returns the item from a list of items at a specified index. … The index is an integer expression that specifies the index of the element to be returned.