Question

I am using MYSQL5.1,Though I tried to find documentation for this but was unsuccessful,secondly I wanted to know logical error in the following query..

SQL QUERY

SELECT date , month , Sum(fact_1) ,
( 2 / Sum(fact_2) ) , 2 FROM( SELECT
time.date, time.month, time.year,
MAX(sales_fact.sell_out_value) as
fact_1, 0 as fact_2 FROM sales_fact,
time_dim as time WHERE
time.id=sales_fact.time_id AND
time.date=”2008-01-01″ GROUP BY
time.date ORDER BY time.year UNION
SELECT time.date, time.month,
time.year, 0 as fact_1,
MAX(sales_target_fact.sell_out_target)
as fact_2 FROM sales_target_fact,
time_dim as time WHERE
time.id=sales_target_fact.time_id AND
time.date=”2008-01-01″ GROUP BY
time.date ORDER BY time.year ) as
Combined_Table GROUP BY date ORDER BY
year

ERROR LINE

• Incorrect usage of UNION and ORDER BY
• Errorcode#1221

Answer 1

The error indicates that your ORDER BY is ambiguous, you need to parenthesize your SELECT statements to indicate to MySQL how it is to be applied.

From the MySQL Docs:

To use an ORDER BY or LIMIT clause to
sort or limit the entire UNION result,
parenthesize the individual SELECT
statements and place the ORDER BY or
LIMIT after the last one.

So, given your query, put each query inside parentheses and place the ORDER BY outside them:

SELECT date , month , Sum(fact_1) , ( 2 / Sum(fact_2) ) , 2 
FROM( 
  (SELECT time.date, time.month, time.year, 
     MAX(sales_fact.sell_out_value) as fact_1, 0 as fact_2 
  FROM sales_fact, time_dim as time 
  WHERE time.id=sales_fact.time_id AND time.date="2008-01-01"
  GROUP BY time.date)
  UNION 
  (SELECT time.date, time.month, time.year, 0 as fact_1,
     MAX(sales_target_fact.sell_out_target) as fact_2
   FROM sales_target_fact, time_dim as time
   WHERE time.id=sales_target_fact.time_id AND time.date="2008-01-01"
   GROUP BY time.date)
   ORDER BY time.year
) as Combined_Table GROUP BY date ORDER BY year

Alternatively, if you wanted the ORDER BY to apply to each statement individually before the UNION, put the ORDER BY within the parentheses for each of the two SELECT statements.

SELECT date , month , Sum(fact_1) , ( 2 / Sum(fact_2) ) , 2 
FROM( 
  (SELECT time.date, time.month, time.year, 
     MAX(sales_fact.sell_out_value) as fact_1, 0 as fact_2 
  FROM sales_fact, time_dim as time 
  WHERE time.id=sales_fact.time_id AND time.date="2008-01-01"
  GROUP BY time.date
  ORDER BY time.year)
  UNION 
  (SELECT time.date, time.month, time.year, 0 as fact_1,
     MAX(sales_target_fact.sell_out_target) as fact_2
   FROM sales_target_fact, time_dim as time
   WHERE time.id=sales_target_fact.time_id AND time.date="2008-01-01"
   GROUP BY time.date
   ORDER BY time.year)
) as Combined_Table GROUP BY date ORDER BY year