SQL is a language used to retrieve, insert, update and delete data from databases. SELECT statements are used to retrieve data from tables, WHERE clauses specify conditions for filtering results, and * can be used to select all columns. DELETE statements remove rows from tables based on specified conditions.

1. SQL

2. SQL
• SQL – Structured Query Language
• You can use SQL for:
• Running queries in a database
• Retrieve data from the database
• Insert/update and delete records in a database

3. SQL SELECT *
• To see all records from a certain table in a database:
• SELECT * FROM table_name;

4. SQL SELECT *
Example
From the table Teachers:
• SELECT * FROM Teacher;
Name Number TutorGroup Subject
Mrs Smith Ext 247 4T1 Maths
Mr Charles Ext 372 2R1 CDT
Miss Kensington Ext 121 1R1 Computing
Dr Wright Ext 450 3B2 Science
Mrs Grey Ext 449 4R1 English
Mr Temple Ext 102 2B1 Maths
Mrs Cloud Ext 546 5T1 French
Mr Stewart Ext 631 6T1 Computing
Mrs Thomas Ext 518 1B2 PE
Mr Singleton Ext 712 6R1 Art

5. SQL SELECT - ORDER BY
• To see certain records from a table in a database:
• SELECT column_names FROM table_name;

6. SQL SELECT - ORDER BY
Example
• SELECT Name, Subject FROM Teachers;
• Answer:
Name Number TutorGroup Subject
Mrs Smith Ext 247 4T1 Maths
Mr Charles Ext 372 2R1 CDT
Miss Kensington Ext 121 1R1 Computing
Dr Wright Ext 450 3B2 Science
Mrs Grey Ext 449 4R1 English
Mr Temple Ext 102 2B1 Maths
Mrs Cloud Ext 546 5T1 French
Mr Stewart Ext 631 6T1 Computing
Mrs Thomas Ext 518 1B2 PE
Mr Singleton Ext 712 6R1 Art
Name Subject
Mrs Smith Maths
Mr Charles CDT
Miss Kensington Computing
Dr Wright Science
Mrs Grey English
Mr Temple Maths
Mrs Cloud French
Mr Stewart Computing
Mrs Thomas PE
Mr Singleton Art

7. SQL DELETE
• To delete a record from a table :
• DELETE FROM table_name WHERE condition;

8. SQL DELETE
Example
• DELETE FROM Teachers WHERE Name = ‘Dr Wright’;
• Answer:
Name Number TutorGroup Subject
Mrs Smith Ext 247 4T1 Maths
Mr Charles Ext 372 2R1 CDT
Miss Kensington Ext 121 1R1 Computing
Dr Wright Ext 450 3B2 Science
Mrs Grey Ext 449 4R1 English
Mr Temple Ext 102 2B1 Maths
Mrs Cloud Ext 546 5T1 French
Mr Stewart Ext 631 6T1 Computing
Mrs Thomas Ext 518 1B2 PE
Mr Singleton Ext 712 6R1 Art
Name Number TutorGroup Subject
Mrs Smith Ext 247 4T1 Maths
Mr Charles Ext 372 2R1 CDT
Miss
Kensington
Ext 121 1R1 Computing
Mrs Grey Ext 449 4R1 English
Mr Temple Ext 102 2B1 Maths
Mrs Cloud Ext 546 5T1 French
Mr Stewart Ext 631 6T1 Computing
Mrs Thomas Ext 518 1B2 PE
Mr Singleton Ext 712 6R1 Art