I'm trying to get a UNION of 3 tables, each of which have 97 fields. I've tried the following:
select * from table1
union all
select * from table2
union all
select * from table3
This gives me an error message:
Too many fields defined.
I also tried explicitly selecting all the field names from the first table (ellipses added for brevity):
select [field1],[field2]...[field97] from table1
union all
select * from table2
union all
select * from table3
It works fine when I only UNION two tables like this:
select * from table1
union all
select * from table2
I shouldn't end up with more than 97 fields as a result of this query; the two-table UNION only has 97. So why am I getting Too many fields with 3 tables?
EDIT: As RichardTheKiwi notes below, Access is summing up the field count of each SELECT query in the UNION chain, which means that my 3 tables exceed the 255 field maximum. So instead, I need to write the query like this:
select * from table1
union all
select * from
(select * from table2
union all
select * from table3)
which works fine.
It appears that the number of fields being tracked (limit 255) is counted against ALL parts of the UNION ALL. So 3 x 97 = 291, which is in excess. You could probably create a query as a UNION all of 2 parts, then another query with that and the 3rd part.
I had two tables with 173 fields each (2 x 173 > 255!). So I had to resort to splitting the tables in half (keeping the primary key in both), before using the UNION statement and reassembling the resulting output tables using a JOIN.
select u1.*, u2.*
from (
select [field1_PKID],[field2],...,[field110]
from table1
union all
select [field1_PKID],[field2],...,[field110]
from table2
) as u1
inner join (
select [field1_PKID],[field111],...,[field173]
from table1
union all
select [field1_PKID],[field111],...,[field173]
from table2
) as u2
on [u1].[field1_PKID] = [u2].[field2_PKID]
Perhaps if your 3 tables have duplicate records you can go with UNION instead of UNION ALL which may reduce the number of fields to be tracked. Because UNION will always serve the business purpose which removes duplicates. In that case your query will be like following,
select * from table1
union
select * from table2
union
select * from table3;
Related
I am trying to union some table. But I am having some issues with the query as I have the following error:
Queries in UNION ALL have mismatched column count; query 1 has 10 columns, query 2 has 12 columns at [3:1]
The query used is:
SELECT * FROM `table_1`
UNION ALL
SELECT * ,null, FROM `table_2`
UNION ALL
SELECT * FROM `table_3`
UNION ALL
SELECT * FROM `table_4`
UNION ALL
SELECT * , null, FROM `table_5`
Please someone have any suggestions?
In a UNION ALL all queries need to be the same number of columns.
You need to post the schema of all tables. But according to the error message you posted, this could help for the 2 first tables:
SELECT *, null FROM `table_1` -- assuming table_1 has 10 columns, add 1 more empty to match the table_2
UNION ALL
SELECT * FROM `table_2` -- assuming table_2 has 11 columns
-- make the same to the rest of queries
-- UNION ALL
-- SELECT * FROM `table_3`
-- UNION ALL
-- SELECT * FROM `table_4`
-- UNION ALL
-- SELECT * , null, FROM `table_5`
Update:
Adding a example of union all declaring the columns:
SELECT
col1_str,
col2_str,
col3_int,
col4_int
FROM `table_1`
UNION ALL
SELECT
col2_str,
FORMAT_DATE("%Y-%m-%d", col1_date) as col1_str, -- transform a date column to string
col3_int,
null
FROM `table_2`
I am trying to create a union with 3 tables that have the same column names. However, the queries tested seems not to be working.
The first query that I have used is the following:
Select * FROM table1
UNION ALL
SELECT * FROM table2
SELECT * FROM table3
UNION ALL
The second query used is the following:
SELECT *
FROM
(select * from table_1),
(select * from table_2),
(select * from table_3)
Both of them are not working for me. Please someone can help me with this?
This should work if columns are identical:
SELECT * FROM table1 UNION ALL
SELECT * FROM table2 UNION ALL
SELECT * FROM table3
It gives me error when i try to join two tables.Both tables has same number of columns
Here is the error
failed to find conversion function from unknown to text
select * from table1
union
select * from table 2;
When you use UNION columns need the same type as the same position.
use clear column name instead of *, Because we can't predict the number of columns after table1 or table2 is different.
select col1,col2...
from table1
union
select col1,col2...
from table2;
So this is fairly common knowledge to select rows from multiple tables and stack the results on top of each other:
SELECT * FROM table1
UNION
SELECT * FROM table2
UNION
...
However, if I want only a limited number of rows from each table, then how should I write it?
SELECT * FROM table1 LIMIT 2
UNION
SELECT * FROM table2 LIMIT 2
UNION
...
Clearly doesn't work.
Note that in my case, I have 51 tables, all with the same exact columns.
could be work this way
( SELECT * FROM table1 LIMIT 2 )
UNION
( SELECT * FROM table2 LIMIT 2 )
UNION
...
I need to return the unique records between two tables. Ideally, an UNION would solve my problem but both tables contain an object field which gives me an error(cannot ORDER objects without MAP or ORDER method) when I do UNION/distinct.
So, I was wondering if I can do a UNION ALL(to avoid the error) to get all the records first then do something to return only the unique records from there. I tried analytic function combined with the UNION ALL query but no luck so far.
Select * from Table1
union all
Select * from table2
Any help? Note:I need to return all fields.
I actually solved the problem using analytic function+row_num. The query will choose the first record for each set of duplicates hence returning only the unique records.
select * from
(
select ua.*,row_number() over (partition by p_id order by p_id ) row_num from
(
select * from table1
union all
select * from table2
)ua
) inner
where inner.row_num=1
How about this :
SELECT DISTINCT A.* FROM
(
Select * from Table1
union all
Select * from table2
) A;
(or)
SELECT col1,col2,col3...coln FROM
(
Select col1,col2,col3...coln from Table1
union all
Select col1,col2,col3...coln from table2
) A
GROUP BY A.col1,col2,col3...coln;
UNION ALL will give duplicate values as well .. instead use UNION and see if you are facing the error