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SQL LEFT JOIN

The SQL left join returns all the values from the left table and it also includes matching values from right table, if there are no matching join value it returns NULL.

BASIC SYNTAX FOR LEFT JOIN:

SELECT table1.column1, table2.column2....
FROM table1 
LEFTJOIN table2
ON table1.column_field = table2.column_field;

let us take two tables in this example to elaborate all the things:

CUSTOMER TABLE:

ID	NAME	AGE	SALARY
1	ARYAN	51	56000
2	AROHI	21	25000
3	VINEET	24	31000
4	AJEET	23	32000
5	RAVI	23	42000

This is second table

ORDER TABLE:

O_ID	DATE	CUSTOMER_ID	AMOUNT
001	20-01-2012	2	3000
002	12-02-2012	2	2000
003	22-03-2012	3	4000
004	11-04-2012	4	5000

join these two tables with LEFT JOIN:

SQL SELECT ID, NAME, AMOUNT,DATE
FROM CUSTOMER
LEFT JOIN ORDER
ON CUSTOMER.ID = ORDER.CUSTOMER_ID;

This will produce the following result:

ID	NAME	AMOUNT	DATE
1	ARYAN	NULL	NULL
2	AROHI	3000	20-01-2012
2	AROHI	2000	12-02-2012
3	VINEET	4000	22-03-2012
4	AJEET	5000	11-04-2012
5	RAVI	NULL	NULL

Next TopicSQL Right Join

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SQL LEFT JOIN