Page 56 - Modular_V2.0_SQL_Flipbook

Table-STU

Adm_no Name Game_id
101 Isha 1000
102 Manish 1001
103 Karan 1002

Select Name, Game_played from STU, GAMES;
Output:
+--------+-------------+
| Name | Game_played |
+--------+-------------+
| Karan | Cricket |
+--------+-------------+
| Manish | Cricket |
+--------+-------------+
| Isha | Cricket |
+--------+-------------+
| Karan | Rugby |
+--------+-------------+
| Manish | Rugby |
+--------+-------------+
| Isha | Rugby |
+--------+-------------+
| Karan | Football |
+--------+-------------+
| Manish | Football |
+--------+-------------+
| Isha | Football |
+--------+-------------+

These outputs shows that that you need some mechanism to produce useful results. As these cross
products are making the data even more ambiguous so lets learn about equi join now.

EQUI JOIN

An Equi Join is a type of SQL join that retrieves rows from two or more tables based on a
condition that tests for equality between columns in the tables. It returns only those rows where

the values in the specified columns are equal. This join is commonly used when the tables have
a common column, such as an ID.

Syntax:
SELECT table1.column1, table2.column2, ...
Output:
FROM table1, table2 '
+-------------+--------+
WHERE table1.common_column = table2.common_column; | Game_played | Name |
+-------------+--------+
Example using tables: STU and GAMES | Cricket | Isha |
+-------------+--------+
Select Game_played, Name | Rugby | Manish |
+-------------+--------+
from GAMES, STU
| Football | Karan |
where GAMES.Game_id = STU.Game_id; +-------------+--------+

Two tables GAMES and STU were joined in the above example of a common key called Game_id.
This is called equi join.

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