Re: Mysql 5.1 union with group by for results
Hi Machiel, On 8/11/2013 20:04, Machiel Richards wrote: Good day all I am hoping someone can assist me in the following. One of our servers were running mysql 5.0 still and as part of a phased upgrade route we have upgraded to version 5.1. However since the upgrade, the query below gives us an error stating that the syntax is incorrect and I simply cant seem to find out what is actually wrong as all tests and changes have been giving us the same. I have tried many suggestions from the net but to no avail. The query is as follows: Using a shorter but equivalent query, you have: (SELECT t.id, t.name, SUM(val) FROM t1 t) UNION (SELECT t.id, t.name, SUM(val) FROM t2 t) GROUP BY t.id, t.name; That does not work in 5.0 either (at least in 5.0.96): ERROR 1064 (42000): 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 'GROUP BY t.id, t.name' at line 4 The issue is that you are trying grouping the entire UNION result, but at that point there is no SELECT any longer - there is just the result set. You are also referencing tables that exists inside each of the SELECT statements, but at the time the GROUP BY is reached, there are no tables. Note that as written the two SELECT parts will also give non-deterministic results as you have an aggregate function but no GROUP BY, so the values of id and val1 will be random. What you probably want instead is either: (SELECT t.id, t.name, SUM(val) FROM t1 t GROUP BY t.id, t.name) UNION (SELECT t.id, t.name, SUM(val) FROM t2 t GROUP BY t.id, t.name); or SELECT a.id, a.name, SUM(val) FROM ( (SELECT t.id, t.name, t.val FROM t1 t) UNION (SELECT t.id, t.name, t.val FROM t2 t) ) a GROUP BY a.id, a.name; On a side note: AND SUBSTRING(t.Day,1,7) = '2013-08' AND SUBSTRING(t.Day,1,7) = '2013-11') Assuming t.Day is a date, datetime, or timestamp column, you can rewrite that WHERE clause to something like (depending on the exact data type): t.Day BETWEEN '2013-08-01 00:00:00' AND '2013-11-30 23:59:59' or t.Day = '2013-08-01 00:00:00' AND t.Day '2013-12-01 00:00:00' That way you will be able to use an index for that condition. Best regards, Jesper Krogh MySQL Support
Re: Mysql 5.1 union with group by for results
- Original Message - From: Machiel Richards machiel.richa...@gmail.com ERROR 1064 (42000): 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 'GROUP BY t.AccountID, I suspect your query has never been doing what you think at all, and you need to select [fields] from ( select fields1 blahblah UNION select fields2 blahblah) unionized group by blurb that is, wrap the entire union in a virtual table and do the group by on that. -- Unhappiness is discouraged and will be corrected with kitten pictures. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: Mysql 5.1 union with group by for results
Happiness, that gave me what I was looking for. Thank you Johan. I have tested the option you gave me but my brackets was in the wrong place. On 08/11/2013 13:23, Johan De Meersman wrote: - Original Message - From: Machiel Richards machiel.richa...@gmail.com ERROR 1064 (42000): 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 'GROUP BY t.AccountID, I suspect your query has never been doing what you think at all, and you need to select [fields] from ( select fields1 blahblah UNION select fields2 blahblah) unionized group by blurb that is, wrap the entire union in a virtual table and do the group by on that. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
Re: Mysql 5.1 union with group by for results
Hi Jesper I was just discussing this with the development manager now and the following was noted. - The query was written for mysql 4.0 originally and it seems that in version 5.0 they had enabled some legacy support stuff ( I am not too familiar with this as it is before my mysql time ;-) ). - I have now explained to them what the problem is and they will be working with the developers to rewrite all these queries. Regards Machiel. On 08/11/2013 13:27, Jesper Wisborg Krogh wrote: Hi Machiel, On 8/11/2013 20:04, Machiel Richards wrote: Good day all I am hoping someone can assist me in the following. One of our servers were running mysql 5.0 still and as part of a phased upgrade route we have upgraded to version 5.1. However since the upgrade, the query below gives us an error stating that the syntax is incorrect and I simply cant seem to find out what is actually wrong as all tests and changes have been giving us the same. I have tried many suggestions from the net but to no avail. The query is as follows: Using a shorter but equivalent query, you have: (SELECT t.id, t.name, SUM(val) FROM t1 t) UNION (SELECT t.id, t.name, SUM(val) FROM t2 t) GROUP BY t.id, t.name; That does not work in 5.0 either (at least in 5.0.96): ERROR 1064 (42000): 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 'GROUP BY t.id, t.name' at line 4 The issue is that you are trying grouping the entire UNION result, but at that point there is no SELECT any longer - there is just the result set. You are also referencing tables that exists inside each of the SELECT statements, but at the time the GROUP BY is reached, there are no tables. Note that as written the two SELECT parts will also give non-deterministic results as you have an aggregate function but no GROUP BY, so the values of id and val1 will be random. What you probably want instead is either: (SELECT t.id, t.name, SUM(val) FROM t1 t GROUP BY t.id, t.name) UNION (SELECT t.id, t.name, SUM(val) FROM t2 t GROUP BY t.id, t.name); or SELECT a.id, a.name, SUM(val) FROM ( (SELECT t.id, t.name, t.val FROM t1 t) UNION (SELECT t.id, t.name, t.val FROM t2 t) ) a GROUP BY a.id, a.name; On a side note: AND SUBSTRING(t.Day,1,7) = '2013-08' AND SUBSTRING(t.Day,1,7) = '2013-11') Assuming t.Day is a date, datetime, or timestamp column, you can rewrite that WHERE clause to something like (depending on the exact data type): t.Day BETWEEN '2013-08-01 00:00:00' AND '2013-11-30 23:59:59' or t.Day = '2013-08-01 00:00:00' AND t.Day '2013-12-01 00:00:00' That way you will be able to use an index for that condition. Best regards, Jesper Krogh MySQL Support -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe:http://lists.mysql.com/mysql
