SQL sum ต้องการใช้คำสั่ง sql สำหรับ sum,count ฯลฯ จากหลายฐานข้อมูล

SELECT sum(total) as use
FROM dbco1.summary, dbco2.summary

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'use FROM dbco1.summary, dbco2.summary' at line 1

SELECT sum(total) as use
FROM dbco1.summary, dbco2.summary

SELECT sum(total) as use
FROM dbco1.summary, dbco2.summary
GROUP BY date

SELECT sum(total) as use
FROM dbco1.summary, dbco2.summary
GROUP BY dbco1.date

#1052 - Column 'total' in field list is ambiguous

#1052 - Column 'summary.total' in field list is ambiguous