SELECT *
FROM
(SELECT Campus_ID AS A_Campus, * FROM A_Campuses
UNION
SELECT Campus_ID AS H_Campus, * FROM H_Campuses
UNION
SELECT Campus_ID AS B_Campus, * FROM B_Campuses)
ORDER BY Campus_Name ASC
It gives the sql error
#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 '* FROM A_Campuses UNION
SELECT Campus_ID AS H_Campus, * FROM
H_Campuses' at line 3
Step 1
You have two syntax errors
not aliasing the derived table.
* cannot be used AFTER a column name, unless you alias the source table
SELECT *
FROM
(SELECT Campus_ID AS A_Campus, A.* FROM A_Campuses A
UNION
SELECT Campus_ID AS H_Campus, H.* FROM H_Campuses H
UNION
SELECT Campus_ID AS B_Campus, B.* FROM B_Campuses B) AS X
ORDER BY Campus_Name ASC
Step 2
But as Phil points out, since you are sub-querying only to do an order by, there is no need to subquery at all. ORDER BY applies to the entire UNION-ed result.
SELECT Campus_ID AS A_Campus, A.* FROM A_Campuses A
UNION
SELECT Campus_ID AS H_Campus, H.* FROM H_Campuses H
UNION
SELECT Campus_ID AS B_Campus, B.* FROM B_Campuses B
ORDER BY Campus_Name ASC
Step 3
The next thing to point out is that A_, H_ and B_ must ALL have compatible structures for the UNION to align properly. It is also worth mentioning that aliasing Campus_ID as different column names has no value. The column names of the resultant result of a UNION is the FIRST name encountered across the UNION parts - in this case all the column names will come from A_Campuses, as well as the additional column A_Campus. In actual fact, you will have two columns A_Campus and Campus_ID which will always hold EXACTLY the same values. What you probably wanted was to indicate the SOURCE of the data: (notice that I have not even bothered to alias the columns for the 2nd and 3rd parts of the UNION)
SELECT 'A' AS Source, A.* FROM A_Campuses A
UNION ALL
SELECT 'H', H.* FROM H_Campuses H
UNION ALL
SELECT 'B', B.* FROM B_Campuses B
ORDER BY Campus_Name ASC
Note
For performance reasons, use UNION ALL instead of UNION, which performs a DISTINCT against the final result. If you had duplicate Campus_ID across different tables, as well as exactly the same record data, UNION results in one of them being removed, whereas UNION ALL keeps both (or all 3) copies. Given the addition of the Source column, this is not a possibility, so using UNION ALL will result in a faster query.
The columns in each branch of the UNION normally need the same name, or will end up with a single name. Also, a sub-select needs an alias (the 'AS C' below), at least in standard SQL; even if you don't mention the alias anywhere else in the query, as below.
I think what you're after is likely:
SELECT *
FROM (SELECT "A" AS Campus_ID, * FROM A_Campuses
UNION
SELECT "H" AS Campus_ID, * FROM H_Campuses
UNION
SELECT "B" AS Campus_ID, * FROM B_Campuses) AS C
ORDER BY Campus_Name ASC
That isn't how you write a union query.
Any ORDER BY clause applies to the union so you don't need to sub-query it. Also, you should aim to have the same column names and aliases across all parts of the union. Your A_Campus, H_Campus and B_Campus aliases will be lost (not sure which one will win out). For example
SELECT Campus_ID, Campus_Name FROM A_Campuses
UNION
SELECT Campus_ID, Campus_Name FROM H_Campuses
UNION
SELECT Campus_ID, Campus_Name FROM B_Campuses
ORDER BY Campus_Name ASC
I'd also refrain from using SELECT * in a union as you need to be specific about what you're selecting.
perhaps more parenthesis are needed
SELECT *
FROM
(
(SELECT Campus_ID AS A_Campus, * FROM A_Campuses)
UNION
(SELECT Campus_ID AS H_Campus, * FROM H_Campuses)
UNION
(SELECT Campus_ID AS B_Campus, * FROM B_Campuses)
)
ORDER BY Campus_Name ASC
Also can you UNION with different column names like that? You might need a fake A_Campus and B_Campus in the H_Campus subquery to get identical columns.
Related
What is wrong with this union? first 'select' and ')' are incorrect
create table GL_ALL
(
select *from GL1
)
UNION
(
select *from GL2
)
UNION
(
select *from GL3
)
UNION
(
select *from GL4
)
UNION
(
select *from GL5
);
That's not the correct syntax for creating a table on the fly in SQL Server, or UNION for that matter.
Assuming that the schemas of each of your tables are the same
SELECT *
INTO GL_ALL FROM GL1 UNION
SELECT * FROM GL2 UNION
SELECT * FROM GL3 UNION
SELECT * FROM GL4 UNION
SELECT * FROM GL5;
As pointed out in comments, this will work for the initial creation of GL_ALL, but not for subsequent inserts after the table is created.
If you need to append to the table at a later time then the sytax changes to:
INSERT INTO GL_ALL
SELECT * FROM GL6;
It's important to realize that the new table will NOT have a primary key nor any foreign keys, indexes (clustered or non), constraints, defaults, etc. that the source tables may have. If these are needed then you will need to manually create them.
And do note the difference between UNION and UNION ALL, where UNION will exclude duplicate rows.
Also note, it's best practice to avoid SELECT * and to specifically call out the columns you want to work with - even if it actually is all columns.
I was recently asked this question and was a little stumped so I want to ask the experts...
Given two tables A & B, I want to return all the values from A and B that do not overlap. Think of two overlapping circles; how do we return all the data that is NOT in the overlapping center section? And, I had to use ANSI Standard SQL rather than Oracle syntax.
Assuming we want everything exclusive to both A & B, my answer was
select *
from A
cross join B
minus
(select a.common_column from a
intersect
select b.common_column)
Does this look correct, or even close? If it is correct, is there a more efficient way to do this?
BTW - my solution was soundly rejected....
Thank you!
Given the tables A and B, you are looking for (A U B) - (A & B). In other words, you need A union B minus their intersection. Remember A and B must be union-compatible for this query to work. I would do:
(select * from A
union
select * from B
)
minus
(select * from A
intersect
select * from B
)
May be full outer join?
select coalesce(A.col, B.col)
from A full outer join B on A.col = B.col
where A.col is null or B.col is null;
For computing a set symmetric difference, you can use a combination of MINUS and UNION ALL:
select * from (
(select * from A
minus
select * from B)
union all
(select * from B
minus
select * from A)
)
Your query was rejected because it is syntactically incorrect: the number of columns differ and it confuses cross join and union all. However, I think you have the right idea for solving this.
You can easily fix this:
(select *
from A
union all
select *
from B
) minus
(select *
from A
intersect
select *
from B
);
That is, combine everything using union all and then subtract the rows that occur in both tables.
Of course, if there is a single id, then you can use the id with join and other operations.
Just like Frank Schmitt answered in the meantime:
Here it is including a data example:
WITH
table_a(name) AS (
SELECT 'From_A_1'
UNION ALL SELECT 'From_A_2'
UNION ALL SELECT 'From_A_3'
UNION ALL SELECT 'From_A_4'
UNION ALL SELECT 'From_A_5'
UNION ALL SELECT 'From_BOTH_6'
UNION ALL SELECT 'From_BOTH_7'
UNION ALL SELECT 'From_BOTH_8'
)
,
table_b(name) AS (
SELECT 'From_B_1'
UNION ALL SELECT 'From_B_2'
UNION ALL SELECT 'From_B_3'
UNION ALL SELECT 'From_B_4'
UNION ALL SELECT 'From_B_5'
UNION ALL SELECT 'From_BOTH_6'
UNION ALL SELECT 'From_BOTH_7'
UNION ALL SELECT 'From_BOTH_8'
)
(SELECT * FROM table_a EXCEPT SELECT * FROM table_b)
UNION ALL
(SELECT * FROM table_b EXCEPT SELECT * FROM table_a)
ORDER BY name
;
name
From_A_1
From_A_2
From_A_3
From_A_4
From_A_5
From_B_1
From_B_2
From_B_3
From_B_4
From_B_5
You will need to select all the data from both tables, except where they overlap, and then combine the data with a union. The code provided should work for your example.
SELECT *
FROM
(
SELECT * FROM Table1
EXCEPT SELECT * FROM Table2
)
UNION
SELECT *
FROM
(
SELECT * FROM Table2
EXCEPT SELECT * FROM Table1
)
Hope this helps.
I encountered just an interesting behaviour of order by clause when query contains union all.
For example I have following query:
select * from dual order by 1
union all
select * from dual
It fails, what the?
Ok it seems that oracle just does not like order by followed by union all. Lets rewrite query to following:
select * from (select * from dual order by 1)
union all
select * from dual
It is fixed!
It will also work if I just swap two queries, so one with order by goes to the end:
select * from dual
union all
select * from dual order by 1
That seems to be inconsistent. So what is the cause of such behaviour? Is it some kind of bug or it is done on purpose?
The statement
select * from (select * from dual order by 1)
has no defined order at all. Only the outermost ORDER BY takes effect in SQL (except if there is a row limit set).
If you still happen to observe order in the query results this is a coincidence that can go away at any time.
In the statement
select * from dual
union all
select * from dual order by 1
The order by is attached to the union all, not the the 2nd select. It is therefore top-level and well-defined.
Use the last form. And put the order by into a new line to make this easier to read.
How can I then sort just single select with union all?
The output order of union all is undefined without order-by clause. Certainly the two inputs are not guaranteed to be concatenated.
select *, 1 as Tag from dual
union all
select *, 2 as Tag from dual
order by Tag, 1 --simulate ordered concatenation of inputs
I have the following problem.
Let TableA(Id int, Name nvarchar(200)) and TableB(Id int, Name nvarchar(200)).
If we run the following query:
SELECT *
FROM
(SELECT *
FROM TableA)
UNION
(SELECT *
FROM TableB)
we get the union of the two datasets.
My Problem is that I want the results of the second dataset to be the ordered by the Name column.
The reason why I need this, is the fact that TableA is a temporary table in my query, that always will hold one record, and this record I want to be the first in the resulting dataset from the union of the two datasets. Also, I want the multiple records of the TableB to be ordered by the Name column.
Unfortunately, when I try to execute the following query
SELECT *
FROM
(SELECT *
FROM TableA)
UNION
(SELECT *
FROM TableB
ORDER BY Name)
I get an ambiguous error message, that informs me that I have an incorrect syntax near the keyword order.
Thanks in advance for any help.
try this:
select id
, name
from
(select 1 as ordercol
, a.id
, a.name
from tableA
union
select 2 as ordercol
, b.id
, b.name
from tableB) i
order by ordercol, name
the error message resulted in you trying to union two subselects. you can put union between two selects that will then be put into a subselect. there is always a select after a union (or union all). i would also suggest you use a union all, that saves time because sql-server will otherwise try and remove records that are in both selects (which in this case is impossible due to the ordercol-column)
i have included a second order-by column that will order the first select before the second. if you order by that first and then by name, you should get the desired result.
select trx_id,refernce number from
(select * from abcd_1_txt union
select * from abcd_2_txt union
select * from abcd_3_txt union
select * from abcd_4_txt)
where trx_id in (123,321,1234)
In the query all the tables are of same format, same column names and same number of columns.
After running this query, surely i will get some data.
My question --- is there any way to know from which of these tables, i am getting the output.
Try to add a column with number of query as below
select qrynum, trx_id,refernce number from
(select 1 as qrynum,* from abcd_1_txt union
select 2,* from abcd_2_txt union
select 3,* from abcd_3_txt union
select 4,* from abcd_4_txt)
where trx_id in (123,321,1234)
as Joe W said in the comment below you can also use name of the table instead of query number, short example:
select tabname, trx_id,refernce number from
(select 'abcd_1_txt' as tabname,* from abcd_1_txt union
...
where trx_id in (123,321,1234)
but both ways don't eliminate duplicates, so you can use union all instead of union. Other way to do that is to run quires separately with the condition
select * from abcd_1_txt where trx_id in (123,321,1234)
select * from abcd_2_txt where trx_id in (123,321,1234)
.
.
.