1. SQL

2. Instructional Objective
To make students aware of SQL commands.
To make them understand different syntax of commands according to condition.
To make them aware of extracting specified information from a table using query.

3. Learning Objective
After studying this lesson the students will be able to
Working of most of the select statement commands.
-State the syntax of making the commands

4. Pre-Requisites
-Students will aware of how to make a table. i.e. create command
They know insert the data into tables.

5. Introduction to SQL Concept of SQL
The user specifies a certain condition.
The program will go through all the records in the database file and select those records that satisfy the condition.(searching).
The result of the query will then be stored in form of a table.

6. Basic structure of an SQL query

7. The Situation: Student Particulars
field type width contents
id numeric student id number
name character name
dob date date of birth
sex character sex: M / F
class character class
hcode character house code: R, Y, B, G
dcode character district code
remission logical fee remission
mtest numeric Math test score

8. Table Structure

9. I General Structure SELECT ...... FROM ...... WHERE ......
SELECT [ALL / DISTINCT] expr1 [AS col1], expr2 [AS col2] ;
FROM table name WHERE condition

10. I General Structure SELECT * FROM student
eg. 1 List all the student records.
SELECT * FROM student
Result

11. I General Structure SELECT name, hcode FROM student WHERE class="1A“;
eg. 2 List the names and house code of 1A students.
SELECT name, hcode FROM student
WHERE class="1A“;
Class 1A 1B : 
Class 1A 1B : 
class="1A"

12. I
General Structure
eg. 2 List the names and house code of 1A students.
Result

13. I General Structure SELECT DISTINCT dcode FROM student
eg. 3 List the residential district of the Red House members.
SELECT DISTINCT dcode FROM student
WHERE hcode="R“;
Result

14. I 1B Girls ? General Structure
eg. 4 List the names and dob of 1B girls.
1B Girls ?

15. I Condition for "1B Girls": 1) class = "1B" 2) sex = "F"
General Structure
eg. 4 List the names and dob of 1B girls.
Condition for "1B Girls":
1) class = "1B"
2) sex = "F"
3) Both ( AND operator)

16. I General Structure SELECT name, dob
eg. 4 List the names and ages (1 d.p.) of 1B girls.
SELECT name, dob
FROM student WHERE class="1B" AND sex="F“;

17. II Comparison SELECT name, mtest FROM student ; WHERE class="1A" AND ;
eg. 5 List the 1A students whose Math test score is between 80 and 90 (incl.)
SELECT name, mtest FROM student ;
WHERE class="1A" AND ;
mtest BETWEEN 80 AND 90
Result

18. II Comparison SELECT name, class FROM student ; WHERE name LIKE "T%"
eg. 6 List the students whose names start with "T".
SELECT name, class FROM student ;
WHERE name LIKE "T%"
Result

19. II Comparison SELECT name, class, hcode FROM student
eg. 7 List the Red house members whose names contain "a" as the 2nd letter.
SELECT name, class, hcode FROM student
WHERE name LIKE "_a%" AND hcode="R“;
Result

20. III Grouping SELECT ...... FROM ...... WHERE condition ;
GROUP BY groupexpr [HAVING requirement]
Group functions:
COUNT( ), SUM( ), AVG( ), MAX( ), MIN( )
– groupexpr specifies the related rows to be grouped as one entry. Usually it is a column.
– WHERE condition specifies the condition of individual rows before the rows are group. HAVING requirement specifies the condition involving the whole group.

21. III
Grouping
eg. 8 List the number of students of each class.

22. 1A 1A 1B 1C 1B 1C Group By Class COUNT( ) COUNT( ) COUNT( ) class 1A
Student
class 1A 1B 1C 1A 1A 1B 1C
COUNT( )
COUNT( ) 1B
COUNT( ) 1C

23. III Grouping SELECT class, COUNT(*) FROM student ; GROUP BY class
eg. 8 List the number of students of each class.
SELECT class, COUNT(*) FROM student ;
GROUP BY class
Result

24. III
Grouping
eg. 10 List the average Math test score of each class.

25. Group By Class
Student
class 1A 1B 1C 1A 1B 1C
AVG( )

26. III Grouping SELECT class, AVG(mtest) FROM student ; GROUP BY class
eg. 12 List the average Math test score of each class.
SELECT class, AVG(mtest) FROM student ; GROUP BY class
Result

27. III Grouping SELECT dcode, COUNT(*) FROM student ;
eg. 13 List the number of girls of each district.
SELECT dcode, COUNT(*) FROM student ;
WHERE sex="F" GROUP BY dcode
Result

28. III Grouping SELECT MAX(mtest), MIN(mtest), dcode ; FROM student ;
eg. 14 List the max. and min. test score of Form 1 students of each district.
SELECT MAX(mtest), MIN(mtest), dcode ;
FROM student ;
WHERE class LIKE "1_" GROUP BY dcode
Result

29. III Grouping SELECT AVG(mtest), class FROM student ;
eg. 15 List the average Math test score of the boys in each class. The list should not contain class with less than 3 boys.
SELECT AVG(mtest), class FROM student ;
WHERE sex="M" GROUP BY class ;
HAVING COUNT(*) >= 3
Result

30. IV Display Order SELECT ...... FROM ...... WHERE ......
GROUP BY ;
ORDER BY colname ASC / DESC

31. IV Display Order SELECT name, id FROM student ;
eg. 16 List the boys of class 1A, order by their names.
SELECT name, id FROM student ;
WHERE sex="M" AND class="1A" ORDER BY name
Result
ORDER BY
dcode

32. IV Display Order SELECT name, id, class, dcode FROM student ;
eg. 17 List the 2A students by their residential district.
SELECT name, id, class, dcode FROM student ;
WHERE class="2A" ORDER BY dcode
Result

33. IV Display Order (in desc. order).
eg. 18 List the number of students of each district
(in desc. order).
SELECT COUNT(*) AS cnt, dcode FROM student ;
GROUP BY dcode ORDER BY cnt DESC
Result

34. IV Display Order SELECT name, class, hcode FROM student ;
eg. 19 List the boys of each house order by the classes. (2-level ordering)
SELECT name, class, hcode FROM student ;
WHERE sex="M" ORDER BY hcode, class

35. IV Display Order Order by class Order by hcode Result : Blue House
Green
House :