If you execute this query
SELECT 'test-a1' AS name1, 'test-a2' AS name2
the result will be a one row-selection with two columns having these values:
test-a1, test-a2
How can I modify the above query to have a selection with several rows, e.g.
test-a1, test-a2
test-b1, test-b2
test-c1, test-c2
I know how to do this with UNION but I feel that there exists a more simple way to do it.
PS. Sorry for such a basic question, it is very hard to google it.
Values keyword can be used as below.
select * from
(values ('test-a1', 'test-a2'), ('test-b1', 'test-b2'), ('test-c1', 'test-c2')) x(col1, col2)
The following will work for SQL:
SELECT 'test-a1' AS name1, 'test-a2' AS name2
UNION ALL
SELECT 'test-b1', 'test-b2'
UNION ALL
SELECT 'test-c1', 'test-c2'
UNION ALL is the best bet. It's faster than UNION and you will have mutually exclusive rows.
Extending the answer of #openshac for oracle, as the below mentioned code works for oracle:
SELECT 'test-a1' AS name1, 'test-a2' AS name2 from dual
UNION ALL
SELECT 'test-b1', 'test-b2' from dual
UNION ALL
SELECT 'test-c1', 'test-c2' from dual
You can use a temp table, fill it up with your results and then select from it
create table #tmpAAA (name1 varchar(10), name2 varchar(10))
insert into #tmpAAA (name1, name2)
values ('test_a', 'test_b'),
('test_c', 'test_d'),
('test_e', 'test_f'),
('test_g', 'test_h'),
('test_i', 'test_j');
select * from #tmpAAA;
This will return
name1 name2
==================
test_a test_b
test_c test_d
test_e test_f
test_g test_h
test_i test_j
I'd love to hear is anyone has a better solution. In the past I've used this:
Select top 3 'Hardcode'
from tableWithLotsOfRows
Would you mind switching abc, with 123?
select top 3
'test-A'+convert(varchar, row_number() over (order by PrimaryKey)),
'test-B'+convert(varchar, row_number() over (order by PrimaryKey))
from tableWithLotsOfRows
that should return something like:
TestA1, Test-B1
TestA2, Test-B2
TestA3, Test-B3
As of MySQL 8.0.19, it is possible to do
SELECT
column_0 AS name1,
column_1 AS name2
FROM
(VALUES
ROW('test-a1','test-a2'),
ROW('test-b1','test-b2'),
ROW('test-c1','test-c2')
) AS hardcodedNames
Which returns
name1 name2
==================
test-a1 test-a2
test-b1 test-b2
test-c1 test-c2
A note on column names
The columns of the table output from VALUES have the implicitly named columns column_0, column_1, column_2, and so on, always beginning with 0.
Documentation here: https://dev.mysql.com/doc/refman/8.0/en/values.html.
The following code work for me in MSSQL environment:
SELECT Name1,Name2 FROM(VALUES ('test-a1', 'test-a2'),
('test-b1', 'test-b2'),
('test-c1', 'test-c2'))AS Test(Name1,Name2)
Output:
Name1 Name2
------- -------
test-a1 test-a2
test-b1 test-b2
test-c1 test-c2
In MySQL you could use UNION like this:
SELECT * from
(SELECT 2006 AS year UNION
SELECT 2007 AS year UNION
SELECT 2008 AS year UNION
) AS years
Related
Is there a function like "unnest" from POSTGRESQL on MYSQL?
Query (PSQL):
select unnest('{1,2,3,4}'::int[])
Result (as table):
int |
_____|
1 |
_____|
2 |
_____|
3 |
_____|
4 |
_____|
Short answer
Yes, it is possible. From technical viewpoint, you can achieve that with one query. But the thing is - most probably, you are trying to pass some logic from application to data storage. Data storage is intended to store data, not to represent/format it or, even more, apply some logic to it.
Yes, MySQL doesn't have arrays data type, but in most cases it won't be a problem and architecture can be created so it will fit those limitations. And in any case, even if you'll achieve it somehow (like - see below) - you won't be possible to properly work later with that data, since it will be just result set. You may store it, of course - so to, let's say, index later, but then it's again a task for an application - so to create that import.
Also, make sure that it is not a Jaywalker case, so not about storing delimiter-separated values and later trying to extract them.
Long answer
From technical viewpoint, you can do it with Cartesian product of the two row sets. Then use a well known formula:
N = d1x101 + d2x102 + ...
Thus, you'll be able to create a "all-numbers" table and later iterate through it. That iteration, together with MySQL string functions, may lead you to something like this:
SELECT
data
FROM (
SELECT
#next:=LOCATE(#separator,#search, #current+1) AS next,
SUBSTR(SUBSTR(#search, #current, #next-#current), #length+1) AS data,
#next:=IF(#next, #next, NULL) AS marker,
#current:=#next AS current
FROM
(SELECT 0 as i UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) as n1
CROSS JOIN
(SELECT 0 as i UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) as n2
CROSS JOIN
(SELECT
-- set your separator here:
#separator := ',',
-- set your string here:
#data := '1,25,42,71',
-- and do not touch here:
#current := 1,
#search := CONCAT(#separator, #data, #separator),
#length := CHAR_LENGTH(#separator)) AS init
) AS joins
WHERE
marker IS NOT NULL
The corresponding fiddle would be here.
You should also notice: this is not a function. And with functions (I mean, user-defined with CREATE FUNCTION statement) it's impossible to get result row set since function in MySQL can not return result set by definition. However, it's not true to say that it's completely impossible to perform requested transformation with MySQL.
But remember: if you are able to do something, that doesn't mean you should do it.
This sample fetchs all "catchwords" from Table data, wich are seperated by ","
Maximum values in the commaseparated list is 100
WITH RECURSIVE num (n) AS (
SELECT 1
UNION ALL
SELECT n+1 FROM num WHERE n<100 -- change this, if more than 100 elements
)
SELECT DISTINCT substring_index(substring_index(catchwords, ',', n), ',', -1) as value
FROM data
JOIN num
ON char_length(catchwords) - char_length(replace(catchwords, ',', '')) >= n - 1
In newer Version of MySQL/MariaDB you can use JSON_TABLE if you can JOIN the elements:
SELECT cat.catchword, dat.*
FROM data dat
CROSS JOIN json_table(concat('[',dat.catchwords, ']')
, '$[*]' COLUMNS(
catchword VARCHAR(50) PATH '$'
)
) AS words
Hey guys i have did some coding in mysql to add a new line value to a row..
SELECT
babe
FROM
(SELECT
concat_ws(' ', 'assword \n') AS babe,
) test;
When i did like this i get an output like
BABE
assword name
What i need is an output like
BABE
assword
name(this would be below assword)
Is there any mysql functions to do this ??...or can i UPDATE the row ??..
I am a newbie in mysql. Hope you guys can help me out..Thanks in advance..
The statement includes a newline character in the babe column. You can confirm this by using the HEX() function to view the character encodings.
For example:
SELECT HEX(t.babe)
FROM ( SELECT CONCAT_WS(' ', 'assword \n') AS babe ) t
On my system, that Will output:
617373776F7264200A
It's easy enough to understand what was returned
a s s w o r d \n
61 73 73 77 6F 72 64 20 0A
(In the original query, there's an extraneous comma that will prevent the statement from running. Perhaps there was another expression in the SELECT list of the inline view, and that was returning the 'name' value that's shown in the example output. But we don't see any reference to that in the outer query.
It's not clear why you need the newline character. If you want to return:
BABE
-----------
asssword
name
That looks like two separate rows to me. But it's valid (but peculiar) to do this:
SELECT t.babe
FROM ( SELECT CONCAT_WS(' ', 'assword \nname') AS babe ) t
FOLLOWUP
Q: i just wanted to know how to add a new row below the assword ..if u know please edit the answer
It's not clear what result you are trying to achieve. The specification, divorced from the context of a use-case, is just bizarre.
A: If I had a need to return two rows: one row with the literal 'assword' and another row "below" it with the literal 'name', I could do this:
( SELECT 'assword' AS some_string )
UNION ALL
( SELECT 'name' AS some_string )
ORDER BY some_string
In this particular case, we can get the ordering we need by a simple reference to the column in the ORDER BY clause.
In the more general case, when there isn't a convenient expression for the ORDER BY clause, I would add an additional column, and perform a SELECT on the resultset from the UNION ALL operation. In this example, that "extra" column is named seq:
SELECT t.some_string
FROM ( SELECT 'assword' AS some_string, 1 AS seq
UNION ALL SELECT 'name', 2
)
ORDER BY t.seq
As another example:
( SELECT 'do' AS tone, 1 AS seq )
UNION ALL ( SELECT 're', 2 )
UNION ALL ( SELECT 'mi', 3 )
UNION ALL ( SELECT 'fa', 4 )
ORDER BY seq
I'd only need to add an outer SELECT if I needed a projection operation (for example, to remove the seq column from the returned resultset.
SELECT t.tone
FROM ( SELECT 'do' AS tone, 1 AS seq
UNION ALL SELECT 're', 2
UNION ALL SELECT 'mi', 3
UNION ALL SELECT 'fa', 4
)
ORDER BY t.seq
For experimental purposes only.
I would like to build a query but not querying data extracted for any table but querying data provided in the query it self. Like:
select numbers.* from (1, 2, 3) as numbers;
or
select numbers.* from (field1 = 1, field2 = 2, field3 = 3) as numbers;
so I can do things like
select
numbers.*
from (field1 = 1, field2 = 2, field3 = 3) as numbers
where numbers.field1 > 1;
If the solution is specific for a database engine could be interesting too.
If you wanted the values to be on separate rows instead of three fields of the same row, the method is the same, just one row per value linked with a union all.
select *
from(
select 1 as FieldName union all
select 2 union all
select 3 union all
select 4 union all -- we could continue this for a long time
select 5 -- the end
) as x;
select numbers.*
from(
select 1 ,2, 3
union select 3, 4, 5
union select 6, 7, 8
union select 9, 10, 11 -- we could continue this for a long time
union select 12, 13, 14 -- the end
) as numbers;
This works with MySQL and Postgres (and most others as well).
[Edit] Use union all rather than just union as you do not need to remove duplicates from a list of constants. Give the field(s) in the first select a meaningful name. Otherwise, you can't specify a specific field later on: where x.FieldName = 3.
If you don't provide meaningful names for the fields (as in the second example), the system (at least MySQL where this was tested) will assign the name "1" for the first field, "2" as the second and so on. So, if you want to specify one of the fields, you have to write expressions like this:
where numbers.1 = 3
Use the values row constructor:
select *
from (values (1),(2),(3)) as numbers(nr);
or using a CTE.
with numbers (nr) as (
values (1),(2),(3)
)
select *
from numbers
where nr > 2;
Edit: I just noticed that you also taggeg your question with mysql: the above will not work with MySQL, only with Postgres (and a few other DBMS)
You can use a subquery without table like so:
SELECT
numbers.*
FROM (
SELECT
1 AS a,
2 AS b,
3 AS c
UNION
SELECT
4,
5,
6
) AS numbers
WHERE
numbers.a > 1
If you like queries to always have a table referenced there is a Psuedo table that always has 1 row and no columns called DUAL, you can use it like so:
SELECT
numbers.*
FROM (
SELECT
1 AS a,
2 AS b,
3 AS c
FROM
DUAL
UNION
SELECT
4,
5,
6
FROM
DUAL
) AS numbers
WHERE
numbers.a > 1
After performing union operator between two tables in which the columns in one of the table are empty the result is displaying from second row... i dont why why is this happening ...? can anyone clarify my doubt?
my tables are sample1 and sample2
Both table contains Id, Empname , Location
data in table is
101 Null NUll
102 aaaa sec
data in table2 is
103 bbbb hyd
102 cccc gdv
Query:
(select EmpName,Location
from sample1)
union
(select EmpName,Location
from sample2)
Output
EMPNAME LOCATION
aaaa sec
bbbb hyd
cccc gdv
To remove the null records from the result, try this:
(select EmpName,Location
from sample1
WHERE EmpName IS NOT NULL
AND Location IS NOT NULL)
union
(select EmpName,Location
from sample2
WHERE EmpName IS NOT NULL
AND Location IS NOT NULL)
Result:
EMPNAME LOCATION
vijay ngdv
suresh hyd
ajay hyd
See result in SQL Fiddle.
EDIT:
I guess the record contains empty string or white spaces instead of null. So try this:
(select EmpName,Location
from sample1
WHERE LENGTH(TRIM(EmpName)) >0
AND LENGTH(TRIM(Location)) >0)
union
(select EmpName,Location
from sample2
WHERE LENGTH(TRIM(EmpName)) >0
AND LENGTH(TRIM(Location)) >0)
See result in SQL Fiddle.
Explanation:
LENGTH(TRIM(EmpName)) will return the length of the field EmpName after removing white spaces from it.
How to perform union operation between two tables?
you have to use union operator with following circumstances,
1.You have similar information in multiple tables and you want to retrieve rows from all of
them at once.
2.You want to select several sets of rows from the same table, but the conditions that
characterize each set aren't easy to write as a single WHERE clause. UNION allows retrieval
of each set with a simpler WHERE clause in its own SELECT statement; the rows retrieved by
each are combined and produced as the final query result.
Note : its not the perfect answer for your question but it helps in understanding of union
operator
please see this http://www.mysqlfaqs.net/mysql-faqs/Funtions-and-Operators/How-does-union-work-in-MySQL
I know that this question has been asked in various forms but my requirement happens to be a bit different.
Suppose I have a table that contains data as follows:
ID NAME VALUE
-----------------------------
1 ABC-2-2 X
2 PQRS-1-3 Y
3 ABC-3-2 Z
4 PQRS-1-4 A
5 PQRS-3-4 B
6 MNO-2-1 C
7 AAA-1 D
8 BBB-2 E
9 CCC-3 F
Now, the output that I'm expecting should look something like this:
ID NAME VALUE
-----------------------------
7 AAA-1 D
2 PQRS-1-3 Y
4 PQRS-1-4 A
8 BBB-2 E
6 MNO-2-1 C
1 ABC-2-2 X
9 CCC-3 F
3 ABC-3-2 Z
5 PQRS-3-4 B
Note that this is not a direct alpha-numeric sort. Instead, the value before the first "-" is ignored and the fields are sorted on what is after the first "-" in the name.
I'm not very familiar with PL/SQL and any kind of help on this would be appreciated.
Thanks.
PS: Note that this should work on both Oracle and MySQL.
For your example this would suffice (Oracle syntax):
ORDER BY SUBSTR(name,4)
If the number of characters before the first hyphen can vary, you can do this (again Oracle syntax):
ORDER BY SUBSTR(name,INSTR(name,'-')+1)
However that won't work if you have codes like:
AAA-10-1
AAA-8-1
AAA-9-1
and expect AAA-10-1 to appear after AAA-9-1. Then you will need to parse it further:
ORDER BY LPAD(SUBSTR(name,INSTR(name,'-')+1, INSTR(name,'-',1,2)-INSTR(name,'-')-1),10,'0'),
LPAD(SUBSTR(name,INSTR(name,'-',1,2)+1),10,'0')
(NB I have used LPAD(x,10,'0') to turn a value like '1' into '0000000001' and so on, rather than use TO_NUMBER since this could fail if there are any non-numerics in your data.)
Example:
with data as
(
select 'AAA-1' name from dual
union all
select 'PQR-1-4' name from dual
union all
select 'PQR-1-3' name from dual
union all
select 'AAA-10-10' name from dual
union all
select 'AAA-10-1' name from dual
union all
select 'AAA-9-10' name from dual
union all
select 'AAA-9-1' name from dual
)
select *
from data
ORDER BY LPAD(SUBSTR(name,INSTR(name,'-')+1, INSTR(name,'-',1,2)-INSTR(name,'-')-1),10,'0'),
LPAD(SUBSTR(name,INSTR(name,'-',1,2)+1),10,'0');
Output:
NAME
---------
PQR-1-3
PQR-1-4
AAA-9-1
AAA-9-10
AAA-10-1
AAA-10-10
AAA-1
And if AAA-1 should come first:
ORDER BY LPAD(SUBSTR(name,INSTR(name,'-')+1, INSTR(name||'-','-',1,2)-INSTR(name,'-')-1),10,'0'),
LPAD(SUBSTR(name,INSTR(name||'-','-',1,2)+1),10,'0') nulls first
Not sure about mysql syntax, but you can do this in oracle:
select * from <your_table>
order by substr(name, 5)
in mssql the syntax of finding your problem is :
select * from mytable order by substring(name,PATINDEX('%-%',name)+1,len(name)-PATINDEX('%-%',name))
SqlFiddle