SQL

Where it is Used?
O It is used to manipulate and maintain Databases with queries.
O This can be benefited on integrating with other programming
languages such as PHP, Python, C, .NET etc
O Examples:-
 SELECT `password` FROM `table_login` WHERE
`username`=‘somevalue’;
 UPDATE table_name SET column1=value1,column2=value2,...
WHERE some_column=some_value;
 SELECT column_name FROM table_name
WHERE column_name BETWEEN value1 AND value2;

Some Query Keywords
O SELECT - extracts data from a database
O UPDATE - updates data in a database
O DELETE - deletes data from a database
O INSERT INTO - inserts new data into a database
O CREATE DATABASE - creates a new database
O ALTER DATABASE - modifies a database
O CREATE TABLE - creates a new table
O ALTER TABLE - modifies a table
O DROP TABLE - deletes a table
O CREATE INDEX - creates an index (search key)
O DROP INDEX - deletes an index

The SQL SELECT Statement
O The SELECT statement is used to select data from a
database.
O The result is stored in a result table, called the
result-set.
O SQL SELECT Syntax
O SELECT column_name,column_name
FROM table_name; and
O SELECT * FROM table_name;

The SQL SELECT DISTINCT Statement
O In a table, a column may contain many duplicate
values; and sometimes you only want to list the
different (distinct) values.
O The DISTINCT keyword can be used to return only
distinct (different) values.
O SQL SELECT DISTINCT Syntax
O SELECT DISTINCT column_name,column_name
FROM table_name;

The SQL WHERE Clause
O The WHERE clause is used to extract only
those records that fulfill a specified
criterion.
O SQL WHERE Syntax
O SELECT column_name,column_name
FROM table_name
WHERE column_name operator value;

The SQL AND & OR Operators
O The AND & OR operators are used to filter
records based on more than one condition.
O The AND operator displays a record if both
the first condition AND the second condition
are true.
O The OR operator displays a record if either
the first condition OR the second condition
is true.

SQL ORDER BY Keyword
O The ORDER BY keyword is used to sort the result-set by
one or more columns.
O The ORDER BY keyword sorts the records in ascending
order by default. To sort the records in a descending
order, you can use the DESC keyword.
O SQL ORDER BY Syntax
O SELECT column_name, column_name
FROM table_name
ORDER BY column_name ASC|DESC, column_name ASC|DESC;

SQL INSERT INTO Statement
O The INSERT INTO statement is used to insert new
records in a table.
O SQL INSERT INTO Syntax
O It is possible to write the INSERT INTO statement
in two forms.
O The first form does not specify the column names
where the data will be inserted, only their values:
O INSERT INTO table_name
VALUES (value1,value2,value3,...);
O The second form specifies both the column names and
the values to be inserted:
O INSERT INTO table_name (column1,column2,column3,...)
VALUES (value1,value2,value3,...);

SQL UPDATE Statement
O The UPDATE statement is used to update
existing records in a table.
O SQL UPDATE Syntax
O UPDATE table_nameSET column1=value1,column2=v
alue2,...WHERE some_column=some_value;
O Notice the WHERE clause in the SQL UPDATE
statement!
The WHERE clause specifies which record or
records that should be updated. If you omit
the WHERE clause, all records will be
updated!

SQL DELETE Statement
O The DELETE statement is used to delete
records in a table.
O The SQL DELETE Statement
O The DELETE statement is used to delete rows
in a table.
O SQL DELETE Syntax
O DELETE FROM table_name
WHERE some_column=some_value;
O Notice the WHERE clause in the SQL DELETE
statement!
The WHERE clause specifies which record or
records that should be deleted. If you omit
the WHERE clause, all records will be
deleted!

The IN Operator
O The IN operator allows you to specify
multiple values in a WHERE clause.
O SQL IN Syntax
O SELECT column_name(s)
FROM table_name
WHERE column_name IN (value1,value2,...);
O

SQL BETWEEN Operator
O The BETWEEN operator selects values within a
range. The values can be numbers, text, or
dates.
O SQL BETWEEN Syntax
FROM table_name
WHERE column_name BETWEEN value1 AND value
2;

SQL JOIN
O An SQL JOIN clause is used to combine rows from two or more tables,
based on a common field between them.
O Example:
SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate FROM
Orders INNER JOIN Customers
ON Orders.CustomerID=Customers.CustomerID;
O INNER JOIN: Returns all rows when there is at least one match in
BOTH tables
O LEFT JOIN: Return all rows from the left table, and the matched rows
from the right table
O RIGHT JOIN: Return all rows from the right table, and the matched
rows from the left table
O FULL JOIN: Return all rows when there is a match in ONE of the
tables

SQL UNION Operator
O The UNION operator is used to combine the result-set of
two or more SELECT statements.
O Notice that each SELECT statement within the UNION must
have the same number of columns. The columns must also
have similar data types. Also, the columns in each SELECT
statement must be in the same order.
O SQL UNION Syntax:
O SELECT column_name(s) FROM table1
UNION
SELECT column_name(s) FROM table2;

SQL SELECT INTO Syntax
O We can copy all columns into the new table:
O SELECT *
INTO newtable [IN externaldb]
FROM table1;
O Or we can copy only the columns we want into the
new table:
INTO newtable [IN externaldb]
FROM table1;

SQL CREATE DATABASE Syntax
O Syntax:
O CREATE DATABASE dbname;
O Database tables can be added with the CREATE
TABLE statement.

The SQL CREATE TABLE
Statement
O CREATE TABLE table_name(
column_name1 data_type(size),
....);
O The column_name parameters specify the names of the
columns of the table.
O The data_type parameter specifies what type of data the
column can hold (e.g. varchar, integer, decimal, date,
etc.).
O The size parameter specifies the maximum length of the
column of the table.

DROP INDEX Statement
O The DROP TABLE Statement
O The DROP TABLE statement is used to delete a table.
O DROP TABLE table_name
O The DROP DATABASE Statement
O The DROP DATABASE statement is used to delete a
database.
O DROP DATABASE database_name
O The TRUNCATE TABLE Statement
O What if we only want to delete the data inside the
table, and not the table itself?
O Then, use the TRUNCATE TABLE statement:
O TRUNCATE TABLE table_name

The ALTER TABLE Statement
O SQL ALTER TABLE Syntax
O To add a column in a table, use the following
syntax:
O ALTER TABLE table_name
ADD column_name datatype
O To delete a column in a table, use the
following syntax (notice that some database
systems don't allow deleting a column):
O ALTER TABLE table_name
DROP COLUMN column_name

SQL

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