Introduction to SQL : Introduction to SQL is explained in the easy way. SQL is a standard language for accessing and manipulating databases.
What is SQL?
- SQL stands for Structured Query Language
- SQL lets you access and manipulate databases
- SQL is an ANSI (American National Standards Institute) standard
What Can SQL do?
- SQL can execute queries against a database
- SQL can retrieve data from a database
- SQL can insert records in a database
- SQL can update records in a database
- SQL can delete records from a database
- SQL can create new databases
- SQL can create new tables in a database
- SQL can create stored procedures in a database
- SQL can create views in a database
- SQL can set permissions on tables, procedures, and views
SQL is a Standard – BUT….
- Although SQL is an ANSI (American National Standards Institute) standard, there are different versions of the SQL language.
- However, to be compliant with the ANSI standard, they all support at least the major commands (such as SELECT, UPDATE, DELETE, INSERT, WHERE) in a similar manner.
Most of the SQL database programs also have their own proprietary extensions in addition to the SQL standard!
Using SQL in Your Web Site
To build a web site that shows data from a database, you will need:
- An RDBMS database program (i.e. MS Access, SQL Server, MySQL)
- To use a server-side scripting language, like PHP or ASP
- To use SQL to get the data you want
- To use HTML / CSS to style the page
- RDBMS stands for Relational Database Management System.
- RDBMS is the basis for SQL, and for all modern database systems such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.
- The data in RDBMS is stored in database objects called tables. A table is a collection of related data entries and it consists of columns and rows.
- Look at the “Customers” table:
SELECT * FROM Customers;
Number of Records: 10
|1||Alfreds Futterkiste||Maria Anders||Obere Str. 57||Berlin||12209||Germany|
|2||Ana Trujillo Emparedados y helados||Ana Trujillo||Avda. de la Constitución 2222||México D.F.||05021||Mexico|
|3||Antonio Moreno Taquería||Antonio Moreno||Mataderos 2312||México D.F.||05023||Mexico|
|4||Around the Horn||Thomas Hardy||120 Hanover Sq.||London||WA1 1DP||UK|
|5||Berglunds snabbköp||Christina Berglund||Berguvsvägen 8||Luleå||S-958 22||Sweden|
|6||Blauer See Delikatessen||Hanna Moos||Forsterstr. 57||Mannheim||68306||Germany|
|7||Blondel père et fils||Frédérique Citeaux||24, place Kléber||Strasbourg||67000||France|
|8||Bólido Comidas preparadas||Martín Sommer||C/ Araquil, 67||Madrid||28023||Spain|
|9||Bon app’||Laurence Lebihans||12, rue des Bouchers||Marseille||13008||France|
|10||Bottom-Dollar Marketse||Elizabeth Lincoln||23 Tsawassen Blvd.||Tsawassen||T2F 8M4||Canada|
- Every table is broken up into smaller entities called fields. The fields in the Customers table consist of CustomerID, CustomerName, ContactName, Address, City, PostalCode and Country.
- A field is a column in a table that is designed to maintain specific information about every record in the table.
- A record, also called a row, is each individual entry that exists in a table.
- For example, there are 91 records in the above Customers table.
- A record is a horizontal entity in a table.
- A column is a vertical entity in a table that contains all information associated with a specific field in a table.