Question

I have following two query both are same but differs only in structure.

First query:

SELECT DISTINCT 
    u.username, r.value, u.amount AS `amount`
FROM 
    Daily_Balance_Updates u
INNER JOIN 
    Role r ON u.role_id = r.id
WHERE 
    u.updated_at = (SELECT MAX(inner_u.updated_at)
                    FROM Daily_Balance_Updates AS inner_u
                    WHERE inner_u.username = u.username
                       && amount > 0
                       && UNIX_TIMESTAMP( inner_u.updated_at ) < UNIX_TIMESTAMP( '2013-1-3 23:59:59' )
)
ORDER BY 
    r.value, UNIX_TIMESTAMP( u.updated_at ) DESC

Works fine in Phpmyadmin

Second query

And same query when I use in Java I declare as follow:

query="SELECT DISTINCT u.username, r.value, u.amount AS `amount' FROM Daily_Balance_Updates     u INNER JOIN Role r ON u.role_id = r.id WHERE u.updated_at = ("
+ "SELECT MAX(inner_u.updated_at) FROM Daily_Balance_Updates AS inner_u WHERE inner_u.username = u.username && amount > 0 && UNIX_TIMESTAMP( inner_u.updated_at ) < UNIX_TIMESTAMP('" +date+" 23:59:59' )) ORDER BY r.value DESC,UNIX_TIMESTAMP( u.updated_at )"

but when I execute it it gives error in both phpmyadmin and java

ERROR

Unknown table ‘u’ in field list

My log:

12:23:17,963 INFO  [STDOUT] 2013-01-07 12:23:17,962 ERROR 
    com.walletplus.report.dao.ReportDaoMysql -  Thread #98  - 
    StatementCallback; bad SQL grammar 
        [SELECT DISTINCT u.username, r.value, u.amount AS `amount' FROM 
            Daily_Balance_Updates u INNER JOIN Role r ON u.role_id = r.id   
            WHERE u.updated_at = (SELECT MAX(inner_u.updated_at) FROM
            Daily_Balance_Updates AS inner_u WHERE inner_u.username = u.username    
            && amount > 0 && UNIX_TIMESTAMP( inner_u.updated_at ) < 
            UNIX_TIMESTAMP('2013-01-01 23:59:59' )) ORDER BY r.value DESC]; 
            nested exception is java.sql.SQLException: Unknown table 'u' in field list

Question:

What is wrong with query? It seems all right.

Answer 1

You have two differences in those two queries

• `amount` vs `amount’, both quotes must be backticks.
  I guess, that’s the reason, why FROM Daily_Balance_Updates u isn’t recognized, and you get the misleading error message.
• order by ... desc, ... vs order by ..., ... desc

Another point, if you have a user_id in addition to username, comparing the user_ids in the where clause would be faster.