Intro to SQL, by Roman Polonsky, software engineer on Google's Global Tools Team. SQL provides powerful but reasonably simple tools for data analysis and handling. This workshop will take absolute beginners through the basics of SQL. You’ll learn SQL queries needed to collect data from a database, even if it lives in different places and analyze it to find the answers you’re looking for. Take away from this workshop the understanding of essential SQL skills that allow developers to write queries against single and multiple tables, manipulate data in tables, and create database objects.

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10. ● Hierarchical
○ 1960s IBM
○ Efficient but complex to implement
History of Databases
● Relational
○ Logically-related entities (tables)
○ Dominant form of storage
○ Major players: Microsoft (Access, SQL Server), Oracle (Oracle, mySQL)
● NoSQL
○ Schemaless
○ Quick to implement
○ Easy to change on the fly
○ Most famous: MongoDB

11. What is SQL
Structured Query Language, the standard method of querying relational databases
Developed in IBM's San Jose research laboratory in the 1970's.
Standardised by ANSI in 1986
Using SQL, you can define
● what data you want to retrieve from the database
● what tables you want to get the data from
● what actions you want to perform on the data
Most major commercial platforms have their own "flavor" of SQL (i.e. ANSI SQL+)
but basic concepts common to all.

12. Structure of relational database
Tables and relationships

13. SQL Standard Commands
● Select
● Insert
● Update
● Delete
● Create
● Drop

14. Table Basics
Column:
● Column name
● Data Type
● Attributes (length, format, etc)
Rows
● Records

15. Format of create table if you were to use optional constraints:
create table "tablename"
("column1" "data type"
[constraint],
"column2" "data type"
[constraint],
"column3" "data type"
[constraint]);
[ ] = optional
Note: You may have as many columns as you'd like, and the constraints are optional.
CREATE Table

16. CREATE Table
Example:
create table employee
(first varchar(15),
last varchar(20),
age number(3),
address varchar(30),
city varchar(20),
state varchar(20));

17. DROP Table
The drop table command is used to delete a table and all rows in the table.
drop table "tablename"
Example:
drop table myemployees_ts0211;
Note: To delete an entire table including all of its rows, issue the drop table command
followed by the tablename. drop table is different from deleting all of the records in the
table. Deleting all of the records in the table leaves the table including column and
constraint information. Dropping the table removes the table definition as well as all of its
rows.

18. INSERT Statement
The insert statement is used to insert or add a row of data into the
table.
insert into "tablename"
(first_column,...last_column)
values (first_value,...last_value);
In the next example, the column name first will match up with the
value 'Luke', and the column name state will match up with the value
'Georgia'.

19. INSERT Statement
Example:
insert into employee
(first, last, age, address, city, state)
values ('Luke', 'Duke', 45, '2130 Boars Nest',
'Hazard Co', 'Georgia');

20. UPDATE Statement
The update statement is used to update or change records that match a specified criteria.
update "tablename"
set "columnname" =
"newvalue"
[,"nextcolumn" =
"newvalue2"...]
where "columnname"
OPERATOR "value"
[and|or "column"
OPERATOR "value"];

21. UPDATE Statement
Examples:
update phone_book
set area_code = 623
where prefix = 979;

22. DELETE Statement
The delete statement is used to delete records or rows from the table.
delete from "tablename"
where "columnname"
OPERATOR "value"
[and|or "column"
OPERATOR "value"];
Examples:
delete from employee
where lastname = 'May';

23. Query Structure
The SELECT statement is used to query the database and retrieve
selected data that match the criteria that you specify. Every SQL query
will have the same basic structure
SELECT <- The fields you want to return
FROM <- The tables the fields live in
select "column1" [,"column2",etc]
from "tablename"

24. WHERE Clause
The Where clause is used to restrict the rows returned by filtering on
specific values
SELECT
FROM
WHERE
SELECT
*
FROM
Employee
WHERE
jobCode = "SFI";

25. JOIN tables
Joins allow you to link data from two or more tables together into a
single query result--from one single SELECT statement.
SELECT "list-of-columns"
FROM table1,table2
WHERE "search-condition(s)"

26. JOIN tables
Example:
SELECT employee_info.employeeid, employee_info.lastname,
employee_sales.commission
FROM employee_info, employee_sales
WHERE employee_info.employeeid = employee_sales.employeeid;

27. Logical operators
The AND operator can be used to join two or more conditions in the
WHERE clause. Both sides of the AND condition must be true in order
for the condition to be met and for those rows to be displayed.
WHERE "condition1" AND "condition2"
The OR operator can be used to join two or more conditions in the
WHERE clause also. However, either side of the OR operator can be
true and the condition will be met - hence, the rows will be displayed.

28. Logical operators
For example:
SELECT employeeid, firstname, lastname, title, salary
FROM employee_info
WHERE salary >= 45000.00 AND title = 'Programmer';

29. Calculations, functions, operators
● Standard math: +, -, /, *
● Math functions: ABS(), ROUND(), etc
● String function*: length (), substr (), upper (), etc
● IN, BETWEEN
Example:
SELECT lastname, round(salary)
FROM emp
WHERE lastname IN ('Hernandez', 'Jones', 'Roberts', 'Ruiz');

30. Aggregative functions
● Max
● Min
● Sum
● Avg
● Count
Example:
SELECT AVG(salary)
FROM employee
WHERE title = 'Programmer'

31. The GROUP BY clause will gather all of the rows together that contain
data in the specified column(s) and will allow aggregate functions to be
performed on the one or more columns. This can best be explained by
an example:
SELECT column1,
SUM(column2)
FROM "list-of-tables"
GROUP BY "column-list"
GROUP BY

32. Let's say you would like to retrieve a list of the highest paid salaries in
each dept:
SELECT max(salary), dept
FROM employee
GROUP BY dept
GROUP BY

33. LIKE Operator
Use this operator to perform string matching
You can also use "%" to specify any number of random characters
SELECT
*
FROM
Employee
WHERE
Lower (lastname) LIKE '%imp%';

34. Other SELECT options
● ORDER BY
● UNION
● LIMIT
● OUTER JOIN
● Sub-queries

35. Table Security
Commands:
● GRANT
● REVOKE
Privileges:
● Read
● Write
● Owner
Level:
● User
● Role/Group
● Schema

36. Other database objects
Indexes
Primary/unique keys
Foreign keys
Views

37. Job roles
Database architect/designer
Database engineer
Database administrator

38. Industry-specific
Popular flavors:
● Oracle - PL/SQL
● Microsoft - Transact-SQL
Popular SQL Tools:
● Toad
● Access

40. Tuesdays & Thursdays
6.30pm - 9pm
Saturdays
9.30am - 3.30pm

41. Mondays &
Wednesdays
6.30pm - 9pm
Saturdays
9.30am - 3.30pm

42. ‘Open
Marketplaces’
‘Products are
about People’