SQL CREATE TABLE is used to create a table.

Syntax

CREATE TABLE table_name

Example

mysql> CREATE TABLE `new_users` (`id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, PRIMARY KEY (`id`));

Query OK, 0 rows affected (0.09 sec)

SQL CREATE DATABASE is used to create a database.

Syntax

CREATE DATABASE database_name

Example

CREATE DATABASE phpcode;

SQL SELECT INTO statement selects data from one table and inserts it into a different table

Mainly it can be used to keep the backup of the table .

Syntax

SELECT *  INTO new_table_name [IN another_DB] FROM old_tablename

SQL UNION can be  used to combine the result  two or more SELECT statements.

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.

Syntax

SELECT column_name(s) FROM table_name1
UNION
SELECT column_name(s) FROM table_name2

MySQL Table – user1

+—-+——+
| id | name |
+—-+——+
|  1 | AAAA |
|  2 | BBBB |
|  3 | CCCC |
|  4 | DDDD |
+—-+——+

MySQL Table – user2

+—-+——+
| id | name |
+—-+——+
|  1 | PPPP |
|  2 | QQQQ |
|  3 | RRRR |
|  4 | RRRR |
+—-+——+

Example

mysql> SELECT * FROM user1 UNION SELECT * FROM user2 ;
+—-+——+
| id | name |
+—-+——+
|  1 | AAAA |
|  2 | BBBB |
|  3 | CCCC |
|  4 | DDDD |
|  1 | PPPP |
|  2 | QQQQ |
|  3 | RRRR |
|  4 | RRRR |
+—-+——+
8 rows in set (0.00 sec)

SQL RIGHT JOIN  returns all the rows from the right table even if there are no matches in the left table

Syntax

SELECT * FROM table_name1 RIGHT JOIN table_name2
ON table_name1.column_name=table_name2.column_name

MySQL Table – users

|+—-+——+
| id | name |
+—-+——+
|  1 | AAAA |
|  2 | BBBB |
|  3 | CCCC |
|  4 | DDDD |
|  5 | EEEE |
+—-+——+

MySQL Table – Orders

+—–+—–+——–+
| oid | uid | items  |
+—–+—–+——–+
|   1 |   1 | Pen    |
|   2 |   2 | Watch  |
|   3 |   3 | shoe   |
|   4 |   4 | mobile |
+—–+—–+——–+

Example

mysql> SELECT u.name,o.items FROM users as u RIGHT JOIN orders as o ON u.id=o.uid ;
+——+——–+
| name | items  |
+——+——–+
| AAAA | Pen    |
| BBBB | Watch  |
| CCCC | shoe   |
| DDDD | mobile |
+——+——–+
4 rows in set (0.00 sec)

SQL LEFT JOIN  returns all rows from the left table even if there are no matches in the right table.

Syntax

SELECT * FROM table_name1 LEFT JOIN table_name2
ON table_name1.column_name=table_name2.column_name

MySQL Table – users

|+—-+——+
| id | name |
+—-+——+
|  1 | AAAA |
|  2 | BBBB |
|  3 | CCCC |
|  4 | DDDD |
|  5 | EEEE |
+—-+——+

MySQL Table – Orders

+—–+—–+——–+
| oid | uid | items  |
+—–+—–+——–+
|   1 |   1 | Pen    |
|   2 |   2 | Watch  |
|   3 |   3 | shoe   |
|   4 |   4 | mobile |
+—–+—–+——–+

Example

mysql> SELECT u.name,o.items FROM users as u LEFT JOIN orders as o ON u.id=o.uid ;
+——+——–+
| name | items  |
+——+——–+
| AAAA | Pen    |
| BBBB | Watch  |
| CCCC | shoe   |
| DDDD | mobile |
| EEEE | NULL   |
+——+——–+
5 rows in set (0.01 sec)

SQL INNER JOIN return rows when there is at least one match in both tables

Syntax

SELECT * FROM table_name1 INNER JOIN table_name2
ON table_name1.column_name=table_name2.column_name

MySQL Table – users
|+—-+——+
| id | name |
+—-+——+
|  1 | AAAA |
|  2 | BBBB |
|  3 | CCCC |
|  4 | DDDD |
|  5 | EEEE |
+—-+——+

MySQL Table – Orders

+—–+—–+——–+
| oid | uid | items  |
+—–+—–+——–+
|   1 |   1 | Pen    |
|   2 |   2 | Watch  |
|   3 |   3 | shoe   |
|   4 |   4 | mobile |
+—–+—–+——–+

Example

mysql> SELECT u.name,o.items FROM users as u INNER JOIN orders as o ON u.id=o.uid ;
+——+——–+
| name | items  |
+——+——–+
| AAAA | Pen    |
| BBBB | Watch  |
| CCCC | shoe   |
| DDDD | mobile |
+——+——–+
4 rows in set (0.00 sec)

SQL JOIN can be used to fetch data from more than one tables based the relationship between columns in tables . Tables are usually related each with primary keys . primary key can be a column with unique value in it .

There are mainly 4 SQL JOINs

JOIN: Return rows when there is at least one match in both tables
LEFT JOIN: Return all rows from the left table, even if there are no matches in the right table
RIGHT JOIN: Return all rows from the right table, even if there are no matches in the left table
FULL JOIN: Return rows when there is a match in one of the tables

SQL AS  can be used to give alias name to a table or a column .

Syntax

For table

SELECT * FROM table_name AS alias_name

For column

SELECT column_name AS alias_name FROM table_name

MySQL Table – users

+—-+——+
| id | name |
+—-+——+
|  1 | PHP  |
|  2 | JS   |
|  3 | HTML |
|  5 | ASP  |
+—-+——+

Example

mysql> SELECT * FROM users as lan;
+—-+——+
| id | name |
+—-+——+
|  1 | PHP  |
|  2 | JS   |
|  3 | HTML |
|  5 | ASP  |
+—-+——+
4 rows in set (0.00 sec)

mysql> SELECT name as lan FROM users;
+——+
| lan  |
+——+
| PHP  |
| JS   |
| HTML |
| ASP  |
+——+
4 rows in set (0.00 sec)