Mysql 120831075600-phpapp01

 The Data Definition Language (DDL) part of SQL
permits database tables to be created or deleted.
We can also define indexes (keys), specify links
between tables, and impose constraints between
database tables.
 CREATE TABLE - creates a new database table
 ALTER TABLE - alters (changes) a database table
 DROP TABLE - deletes a database

 SQL (Structured Query Language) is a syntax
for executing queries. But the SQL language
also includes a syntax to update, insert, and
delete records.
 SELECT - extracts data from a database
table
 UPDATE - updates data in a database table
 DELETE - deletes data from a database table
 INSERT INTO - inserts new data into a
database table

 To create a database:
 SYNTAX
 CREATE DATABASE database_name ;
 EXAMPLE
 CREATE DATABASE s2i;
 To activate the created database:
 SYNTAX
 USE DATABASE_NAME;

 SYNTAX
 CREATE TABLE table_name(column_name1
data_type,column_name2 data_type,.......) ;

Data Type Description
integer(size)
int(size)
smallint(size)
tinyint(size)
Hold integers only. The maximum
number of digits are specified in
parenthesis.
decimal(size,d)
numeric(size,d
)
Hold numbers with fractions. The
maximum number of digits are
specified in "size". The maximum
number of digits to the right of the
decimal is specified in "d".
char(size) Holds a fixed length string (can
contain letters, numbers, and special
characters). The fixed size is
specified in parenthesis.
varchar(size) Holds a variable length string (can
contain letters, numbers, and special
characters). The maximum size is
specified in parenthesis.
date(yyyymmd
d)
Holds a date

 The INSERT INTO statement is used to insert
new rows into a table.
 SYNTAX
 INSERT INTO table_name VALUES (value1,
value2,....) ;
 INSERT INTO table_name (column1,
column2,...)VALUES (value1, value2,....) ;

 The UPDATE statement is used to modify the
data in a table.
 SYNTAX
 UPDATE table_name SET column1=
new_value WHERE
Old_column1=old_value;

 The ALTER TABLE statement is used to add or
drop columns in an existing table.
 SYNTAX
 ALTER TABLE table_name ADD column_name
data_type;

 The DELETE statement is used to delete rows
in a table.
 Syntax
 DELETE FROM table_name WHERE
column_name = some_value;

 Delete All Rows
 DELETE FROM table_name;
 OR
 DELETE * FROM table_name;
 OR
 TRUNCATE TABLE table_name;

 To delete a table
 DROP TABLE table_name;
 To delete a database
 DROP DATABASE database_name;
 To delete the column in table
 ALTER TABLE table_name DROP COLUMN
column_name;

 The SELECT statement is used to select data
from a table. The tabular result is stored in a
result table (called the result-set).
 Select a table fully
 Syntax
 SELECT * FROM Persons;

 SELECT A COLUMN
 Select column_name from table_name;
 SELECT A ROW
 Select*from table_name where
column_name=‘value’;

 All values stored in mysql is in array formate.
 $var1=mysql_query(“select*from table_name”,
$connection_name);
 While($var=mysql_fetch_array($var1))
 {
 Echo “<br/>”;
 Echo $var[‘column_name’];
 }

 The LIKE & UNLIKE condition is used to
specify a search for a pattern in a column.
 Syntax
 SELECT column FROM table_name WHERE
column_name LIKE pattern;
 SELECT column FROM table_name WHERE
column_name UNLIKE pattern;

 EXAMPLES
 SELECT * FROM table_name WHERE column_name
LIKE 'O%‘;
LIKE '%a‘;
LIKE '%la%‘;

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

 SELECT * FROM table_name WHERE
column1=‘value' AND column2=‘value‘;
column1=‘value1' OR column1=‘value2‘;
column1=‘value' AND (column2=‘value1' OR
column2=‘value2‘);

 The ORDER BY keyword is used to sort the
result-set by a specified column.
 The ORDER BY keyword sort the records in
ascending order by default.
 If you want to sort the records in a descending
order, you can use the DESC keyword.

 SELECT column_name(s) FROM table_name
ORDER BY column_name(s) ASC|DESC;
 SELECT * FROM table_name ORDER BY
column_name;
 SELECT * FROM table_name ORDER BY
column_name DESC;

 Auto-increment allows a unique number to be
generated when a new record is inserted into a
table.
 CREATE TABLE Persons ( Id int (5)
AUTO_INCREMENT)
 ALTER TABLE Persons AUTO_INCREMENT=100 ;

 The TOP clause is used to specify the number
of records to return.
 The TOP clause can be very useful on large
tables with thousands of records. Returning a
large number of records can impact on
performance.
 Note: Not all database systems support the
TOP clause.

 SELECT column_name(s) FROM table_name LIMIT
number;
 SELECT TOP 2 * FROM table_name;
 SELECT TOP 50 PERCENT * FROM table_name;

 With SQL, aliases can be used for column names
and table names.
 SELECT column AS column_alias FROM table;
 EXAMPLES: SELECT LastName AS Family, FirstName
AS NameFROM Persons;
 SELECT column FROM table AS table_alias;
 EXAMPLE: SELECT LastName, FROM Persons AS
Employees;

 The IN operator allows you to specify multiple
values in a WHERE clause.
 SELECT column_name(s) FROM table_name WHERE
column_name IN (value1,value2,...);
 SELECT * FROM table_name WHERE column IN
(‘value1',‘value2');

 The BETWEEN operator selects a range of data
between two values. The values can be numbers,
text, or dates.
column_name BETWEEN value1 AND value2;
column_name NOTBETWEEN value1 AND value2;

 To select only DIFFERENT values from the
column named
 SYNTAX
 SELECT DISTINCT Company FROM Orders;

 Constraints are used to limit the type of data
that can go into a table.
 Constraints can be specified when a table is
created (with the CREATE TABLE statement) or
after the table is created (with the ALTER
TABLE statement).
 NOT NULL
 UNIQUE
 CHECK
 PRIMARY KEY
 FOREIGN KEY
 DEFAULT

 The NOT NULL constraint enforces a column
to NOT accept NULL values.
 CREATE TABLE Persons ( P_Id int NOT NULL,
LastName varchar(255) NOT NULL, FirstName
varchar(255), Address varchar(255), City
varchar(255) )

 The UNIQUE constraint uniquely identifies each
record in a database table.
varchar(255), UNIQUE (P_Id) );
 Alter table table_name ADD UNIQUE (ID);

 The PRIMARY KEY constraint uniquely
identifies each record in a database
table.
 Primary keys must contain unique values.
 A primary key column cannot contain
NULL values
 CREATE TABLE Persons ( P_Id int NOT
NULL, LastName varchar(255) NOT NULL,
PRIMARY KEY (P_Id) )
 ALTER TABLE Persons ADD PRIMARY KEY
(P_Id)

 A FOREIGN KEY in one table points to a
PRIMARY KEY in another table.
 CREATE TABLE Orders ( O_Id int NOT NULL,
OrderNo int NOT NULL, P_Id int, PRIMARY
KEY (P_Id), FOREIGN KEY (O_Id) REFERENCES
Persons(P_Id) )
 ALTER TABLE Orders ADD FOREIGN KEY (O_Id)
REFERENCES Persons(P_Id)

 The CHECK constraint is used to limit the value
range that can be placed in a column.
varchar(255), CHECK (P_Id>0) )
 ALTER TABLE Persons ADD CHECK (P_Id>0)

 The DEFAULT constraint is used to insert a
default value into a column.
City varchar(255) DEFAULT 'Sandnes' )
 ALTER TABLE Persons WHERE City SET
DEFAULT 'SANDNES'

 An index can be created in a table to find
data more quickly and efficiently.
 CREATE INDEX index_name ON table_name
(column_name);
 CREATE UNIQUE INDEX index_name ON
table_name (column_name);
 Drop INDEX index_name FROM TABLE_NAME;

 The JOIN keyword is used in an SQL statement to
query data from two or more tables, based on a
relationship between certain columns in these
tables.
 Different SQL JOINS
 INNER JOIN
 OUTER JOIN
 FULL JOIN

 The INNER JOIN keyword return rows when
there is at least one match in both tables.
 SELECT column_name(s) FROM table_name1
INNER JOIN table_name2 ON
table_name1.column_name=table_name2.col
umn_name

 The LEFT JOIN keyword returns all rows from
the left table (table_name1), even if there
are no matches in the right table
(table_name2).
LEFT JOIN table_name2 ON
umn_name

 The RIGHT JOIN keyword Return all rows
from the right table (table_name2), even if
there are no matches in the left table
(table_name1).
RIGHT JOIN table_name2 ON
umn_name

 The FULL JOIN keyword return rows when
there is a match in one of the tables.
FULL JOIN table_name2 ON
umn_name

SQL aggregate functions return a single value,
calculated from values in a column.
 AVG() - Returns the average value
 COUNT() - Returns the number of rows
 FIRST() - Returns the first value
 LAST() - Returns the last value
 MAX() - Returns the largest value
 MIN() - Returns the smallest value
 SUM() - Returns the sum

SQL scalar functions return a single value, based
on the input value.
 UCASE() - Converts a field to upper case
 LCASE() - Converts a field to lower case
 MID() - Extract characters from a text field
 LEN() - Returns the length of a text field
 ROUND() - Rounds a numeric field to the number
of decimals specified
 NOW() - Returns the current system date and
time
 FORMAT() - Formats how a field is to be
displayed

 GROUP BY... was added to SQL because
aggregate functions (like SUM) return the
aggregate of all column values every time
they are called, and without the GROUP BY
function it was impossible to find the sum for
each individual group of column values.

 SELECT column, SUM(column) FROM table GROUP
BY column;
 EXAMPLE: SELECT Company, SUM(Amount) FROM
Sales;
 SELECT Company, SUM(Amount) FROM Sales
GROUP BY Company;
 SELECT column, SUM(column) FROM table GROUP
BY column HAVING SUM(column) condition value;

Statement Syntax
AND / OR SELECT column_name(s)
FROM table_name
WHERE condition
AND|OR condition
ALTER TABLE (add
column)*//
ALTER TABLE table_name
ADD column_name datatype
ALTER TABLE (drop
column)
ALTER TABLE table_name
DROP COLUMN column_name
AS (alias for column) SELECT column_name AS column_alias
FROM table_name
AS (alias for table) SELECT column_name
FROM table_name AS table_alias
BETWEEN SELECT column_name(s)
FROM table_name
WHERE column_name
BETWEEN value1 AND value2
CREATE DATABASE CREATE DATABASE database_name
CREATE INDEX CREATE INDEX index_name
ON table_name (column_name)

CREATE TABLE CREATE TABLE table_name
(
column_name1 data_type,
column_name2 data_type,
.......
)
CREATE UNIQUE INDEX CREATE UNIQUE INDEX
index_name
ON table_name (column_name)
CREATE VIEW CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition
DELETE FROM DELETE FROM table_name
(Note: Deletes the entire table!!)
or
DELETE FROM table_name
WHERE condition
DROP DATABASE DROP DATABASE database_name
DROP INDEX DROP INDEX table_name.index_name
DROP TABLE DROP TABLE table_name

GROUP BY SELECT
column_name1,SUM(column_name2)
FROM table_name
GROUP BY column_name1
HAVING SELECT
column_name1,SUM(column_name2)
FROM table_name
GROUP BY column_name1
HAVING SUM(column_name2)
condition value
IN SELECT column_name(s)
FROM table_name
WHERE column_name
IN (value1,value2,..)
INSERT INTO INSERT INTO table_name
VALUES (value1, value2,....)
LIKE SELECT column_name(s)
FROM table_name
WHERE column_name
LIKE pattern

ORDER BY SELECT column_name(s)
FROM table_name
ORDER BY column_name
[ASC|DESC]
SELECT SELECT column_name(s)
FROM table_name
SELECT * SELECT *
FROM table_name
SELECT DISTINCT SELECT DISTINCT
column_name(s)
FROM table_name
SELECT INTO
(used to create backup copies
of tables)
SELECT *
INTO new_table_name
FROM original_table_name
or
INTO new_table_name

SELECT INTO
(used to create backup copies of tables)
SELECT *
INTO new_table_name
or
INTO new_table_name
TRUNCATE TABLE
(deletes only the data inside the table)
TRUNCATE TABLE table_name
UPDATE UPDATE table_name
SET column_name=new_value
[, column_name=new_value]
WHERE column_name=some_value
WHERE SELECT column_name(s)
FROM table_name
WHERE condition

Mysql 120831075600-phpapp01

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