SQL

Data type

Specifies the type of data that a column can hold (e.g., text and numbers).

Table

Structured file containing rows and columns.

Syntax Rules

Syntax refers to the rules that govern how a programming language must be written.

LIKE operator

A character operator. When used in conjunction with asterisks or brackets, matches parts of a value within a table.

Database

A collection of electronically stored organized files.

Pprimary key

A field whose value uniquely identifies every row in a table.

NOT operator

A logical operator used to match any condition opposite of the one defined.

IN operator

A miscellaneous operator that provides a shorter method for specifying a range of conditions.

Server

A multiple-user computer that provides shared database connection, interfacing, and processing services.

Query

A question or command you pose concerning data from the database.

Row

A record that represents a collection of information relating to an item in a table.

Parts of a query include the following: Clause

A segment of an SQL statement combined to form a complete SQL statement.

Client

A single-user computer that interfaces with the multiple-user server.

Client/server database system

A system that divides processing between client computers and a database server.

Normalization

A three-step technique used to organize data attributes in a more efficient, reliable, flexible, and maintainable structure.

Field

Column that runs vertically within a table.

Parts of a query include the following: Statement

Keywords and data supplied within an SQL query.

Foreign key

Link records of one type with those of another type.

SQL Defined

SQL is a nonprocedural language that is used to manipulate and retrieve data from relational DBMSs such as Microsoft Access, DB2, Sybase, and Microsoft SQL Server. It is considered nonprocedural because of the way operations are carried out. Unlike procedural computer languages like Basic and C, which are concerned with how to perform operations, SQL describes what needs to be processed. The focus is on what to retrieve, delete, or insert.

Arithmetic Operators

Plus (+) Minus (-) Divide (/) Modulus (%) Multiply (*)

Parts of a query include the following: Keywords

Reserved words that allow you to communicate with a database.

ORDER BY clause

Retrieves the name of one or more columns from the SELECT statement, and sorts (ascending or descending) the output.

Sorting Data Using the WHERE Clause

The ability to sort data further enhances the data-retrieval process. Sorting data involves filtering and arranging retrieved data in a customized fashion. In SQL, this is achieved by using the following clauses: GROUP BY HAVING ORDER BY STARTING WITH WHERE

Comparison Operators

The comparison operators are used to compare expressions. An expression is any data type that returns a value

Keys

Uniquely identify a row or record in a table.

ASC keyword

Used to sort data in ascending order.

DESC keyword

Used to sort data in descending order

Keywords: SELECT keyword

Used to tell the database which column(s) to display.

Keywords: FROM keyword

Used to tell the database which table to retrieve the columns from.

Asterisk wildcard character (*)

When used with the LIKE operator, you can match any number of occurrences of any character.

Brackets wildcard character ( [] )

When used with the LIKE operator, you can specify a set of characters that match a character in a specific position.