This document provides an overview of SQL concepts including: - Data types like char, varchar, and null - Core SQL commands like select, update, delete, truncate, and alter - Joins like inner, left, and cross joins - Transaction control with commit, rollback, and savepoints - Exception handling and the ACID properties of transactions - Other objects like views, sequences, indexes, and stored procedures

1. SQL LECTURE

2. HOW SQL WORKS

3. Inside the server

4. Objects in a database

5. Creating a table

6. Core SQL Commands

7. DCL Command(Not to be used by us)

8. Data Types

9. Datatype – Char(30) & Varchar
Char is better than Varchar in terms of processing speed but varchar is more memory efficient than char

10. Selection of data type
Need to understand all the data types to create a table with proper datatype for proper optimization

11. Summary
• Rest of the data types were explained which are available on LMS.
• Whenever you open the client for SQL you have to mention which
database you have to use within the server. Eg- use mydb (database name)
• Client s/w doesn’t store any data on it, its always stored on the server.
• WARNING- if you execute same command twice, it gets executed
multiple times and it might result in addition of unnecessary data.
• Values should be added in same exact order as table column name

12. ‘NULL’ Datatype.
Null is not 0.
Null signifies unknown value.
Can be used only with ‘is not’ command.

13. DDL commands
• DDL command is Data Definition Language command, used to define
a type of dataset for table creation and modification of a table only
• ‘DR CAT’
• D - DROP
• R - RENAME
• C - CREATE
• A - ALTER
• T - TRUNCATE

14. Use and format of ALTER & RENAME

15. TRUNCATE command
• Truncate command deletes the entire Data or the Table content.
• It internally executes 2 commands
• Drops table entirely
• Create fresh table with similar column
• Truncate command cannot be rolled back.
• Truncate comment will delete all the objects created above the table.

16. DML commands
• DML command stands for Data Manipulation Language
• Used to manipulate data within the table
• It is used to modify the data within the table
• DML commands
• Insert – to insert data
• Update – to update existing data
• Delete – to delete the record in data.

17. Alternate way to use INSERT command
• When we don’t know the values of multiple data and want to put
NULL data type we can use the format to specify the data input.

18. ‘Where’ clause in DML & DQL command

19. ‘Update’ command

20. ‘WHERE’ clause
• Where clause is used to define a condition in a query or specific record
• Type1- update students set sname = 'Thomas' where std_id = 1;
• Type2- update students set course = ‘analytics’, marks = 25 where
sname = ‘Thomas’
• Type3- update students set course = ‘ analytics’ (all change)
• For NULL- update students set marks = 0 where course is null
‘HAVING’ clause
• Having clause is used to select specific groups

21. ‘Delete’ command
• Syntax is similar to ‘update’ command
• Delete from students where std_id = 1;
• Delete from students, (will delete all the table records)

22. DQL command – Select (will be used 85%*)
• Different ways to use select command
• Select * from myemp ; – shows everything
• Select count(*) from myemp ; – shows count of rows
• Select * from myemp limit 5 ; – limits data to 5 rows;
• Select first_name, last _name,salary from myemp limit 10 ;

23. Function of ‘SELECT’
• Select does not make any change in the backend.
• It just shows you the desired output
• Can help you make derived column(temp column)
• Select first_name, last _name,salary, salary*0.2 from myemp limit 10 ;
• We can use other arethmatic operators with ‘where’ clause.
• select * from myemp where salary >= 10000;
• select first_name,last_name,job_id,salary from myemp where salary >=
15000;
• IN,BETWEEN,LIKE operators also exist for convenience

24. Result table for AND & OR & IN operator
select * from myemp where dep_id in (20,40,60);
#use IN operator for multiple condition of same column

25. Pattern matching for LIKE operator
select * from myemp where first_name like 'j%'; #name starts with J
select * from myemp where first_name like '%a'; #name ends with A

26. Sorting the table – ‘ORDER BY’
• Order by clause is used ro sort the table according to particular
column
• Select * from myemp order by dep_id; - by default Ascending
• Select * from myemp order by dep_id desc;
Distinct function
• To find out unique values in a table
• Select distinct dep_id from myemp;

27. String functions & operators
• CONCAT()
• LEFT
• RIGHT()
• LOWER()
• UPPER()
https://dev.mysql.com/doc/refman/8.0/en/string-functions.html
Link for all string functions that can be used

28. Date & Time functions
• ADDDATE()
• ADDTIME()
• CURDATE()
• CURTIME()
• NOW()
https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html
Link for all DATE functions that can be used

29. Group functions
• SUM()
• AVG()
• MIN()
• MAX()
• STD()

30. JOINS in mySQL
• INNER JOIN
• LEFT JOIN
• RIGHT JOIN
• CROSS JOIN
• SELF JOIN
• THE RESULTANT TABLE THAT WILL BE CREATED IS THE VIRTUAL TABLE
RESPECTIVE OF THE TYPE OF JOIN USED.

31. JOINS

32. INNER JOIN

33. LEFT Join

34. CROSS Join
• It is irrespective to the common record.
• Will join each record of left table to the corroponding each record of
the right table.

35. Using “PREFIX” and Alias Name
• Its efficient to use prefix to be desprictive
• Eg- select meals.mealname, drinks.drinkname
• Alias name can be used if we are going to use similar name name
multiple times in a table
• We can use alias name for large table names to reduce the size of the
query.
• Eg- select d.drinks, m.meals from drinks as d cross join meals as m;

36. SELF JOIN

37. Data Constraints

38. Command example

39. Concept of primary key

40. Relations between parent and child table

41. Create parent and Child Table

42. TCL - Transaction control language

43. Transaction-Except/Rollback/Savepoint/commit
• Transaction/except – turns off autocommit and executes data or
terminates.
• Rollback – works like undo. Will work only if autocommit is off.
• Savepoint – creates savepoint for rollback in between transaction.
• Commit- Commit the data typed. We cant rollback once commitment
is done.

44. Exception Handling

45. Exceptional Handeling Format

46. COMMIT & ROLLBACK

47. A.C.I.D rule

48. Views
Can be used on “select’ to create a virtual table to select particular paramaters
in a table but editing the view will also edit the main table
Hyperlink- All about Views

49. SEQUENCE object
• Mysql doesn’t have a feature of creating a sequence hence we have
to create a sequence implicitly.
• create table mytab (id integer primary key auto_increment,name
varchar (30),age integer);

50. INDEX
• Performance of the query is improved.
• Search and Retrieval of data becomes faster.
• Indexes youtube video

51. Stored Procedures
• Variables- Parameters & Local Variables
• Local variables – are the variabls that a re written and declared within
the procedure.
• Create a procedure in procedures tabs in schemas
• Stored Procedures is used to make a function
Parameters Local Variables

52. LOOPS