Join multiple tables without duplicate row - mysql

Question

I would like to select 3 tables with the code number is 777
Table 1
Employee code Company Name
001 a
002 b
Table 2
Employee code Voucher NO Date Amount
001 123 12-4-14 100
001 456 2-5-14 500
002 789 3 -7 14 300
Table 3
Voucher No Tax amt code
123 50 777
789 100 888
The output should be
Company Name Employee code Voucher No Date Amount Tax amt code
a 001 123 12-4-14 100 50 777
a 001 456 2-5-14 500 null null
but there are duplicate row when apply the query
SELECT DISTINCT
table1.COMPANY_NAME,
table2.EMPLOYEE_CODE,
table2.VOUCHER_NO,
table2.DATE,
table2.AMOUNT,
table3.TAX_AMT,
table3.CODE
FROM table2
INNER JOIN table1 ON (table2.EMPLOYEE_CODE = table1.EMPLOYEE_CODE)
INNER JOIN table3 ON (table2.VOUCHER_NO = table3.VOUCHER_NO )
WHERE table3.CODE = '777'
The output from the above query
Company Name Employee code Voucher No Date Amount Tax amt code
a 001 123 12-4-14 100 50 777
a 001 456 2-5-14 500 **50 777**
I got try to use DISTINCT but since no work well. Please kindly help what problem with my query.

Answer 1

Try this :
SELECT
table1.COMPANY_NAME,
table2.EMPLOYEE_CODE,
table2.VOUCHER_NO,
table2.DATE,
table2.AMOUNT,
table3.TAX_AMT,
table3.CODE
FROM table1
INNER JOIN table2 ON (table2.EMPLOYEE_CODE = table1.EMPLOYEE_CODE)
LEFT JOIN table3 ON (table2.VOUCHER_NO = table3.VOUCHER_NO )
HAVING
(table3.CODE = '777' OR table3.CODE IS NULL)
Leave me a comment if you need something else, or if you have a specific issue.

Answer 2

Your example output wasn't produced by your SQL command since you use WHERE statement to filter.
If you need to output only 777 code you should use LEFT JOIN with condition instead of WHERE
.....
FROM table2
INNER JOIN table1 ON (table2.EMPLOYEE_CODE = table1.EMPLOYEE_CODE)
LEFT JOIN table3 ON (table2.VOUCHER_NO = table3.VOUCHER_NO )
AND (table3.CODE = '777')

Answer 3

Your second row in your output maybe because it has the same EMPLOYEE_CODE in table2, so I think this may the query that you want:
SELECT
table1.COMPANY_NAME,
table2.EMPLOYEE_CODE,
table2.VOUCHER_NO,
table2.DATE,
table2.AMOUNT,
table3.TAX_AMT,
table3.CODE
FROM table2
INNER JOIN table1 ON (table2.EMPLOYEE_CODE = table1.EMPLOYEE_CODE)
LEFT JOIN table3 ON (table2.VOUCHER_NO = table3.VOUCHER_NO )
WHERE table1.EMPLOYEE_CODE IN
(SELECT table2.EMPLOYEE_CODE
FROM table2 INNER JOIN table3 ON (table2.VOUCHER_NO = table3.VOUCHER_NO)
WHERE table3.code = '777')