I have a query, a generalized version of which I've reproduced below:
SELECT TT.column
FROM Table1 TT
JOIN Table2 T USING (PRIMARYKEY)
GROUP BY T.Date
I want to take the output of this query -- a single column output with multiple rows sorted by date -- and group concat it in another query as a derived table:
SELECT
T.column2,
GROUP_CONCAT(
SELECT TT.column
FROM Table1 TT
JOIN Table2 T USING (PRIMARYKEY)
GROUP BY T.Date) AS concat_output
FROM Table1 TT
JOIN Table2 T USING (PRIMARYKEY)
GROUP BY T.Date
However, this returns an error at the line of the GROUP_CONCAT command.
Thoughts on how to make this work?
EDIT: To give some more detail on why I wanted the derived table to work:
At the moment, without using GROUP_CONCAT, I get multiple rows that look like
a
a
b
b
a
a
c
c
d
a
If I try to GROUP_CONCAT as described by Mukesh's answer, using DISTINCT I get the following, for example, as a row: a, b, c, d when really I want a,b,a,c,d,a.
Thoughts?
Try this query
SELECT
T.column2,
GROUP_CONCAT(
DISTINCT TT.column
) AS concat_output
FROM Table1 TT
JOIN Table2 T USING (PRIMARYKEY)
GROUP BY T.Date
More detail to refer this link
http://www.mysqltutorial.org/mysql-group_concat/
Related
I have 2 sql table as follows:
First table t1:
Second table t2:
I need to calculate the count of "Number" column based on "Name" column from t1 and merge it with t2.
I wrote following code. But it seems not working
select *
from (
select Name, count(Number) as count
from t1
group by Name ) as a
join ( select *
from t2 ) as b
on a.Name = b.Name;
Can any one figure out what is wrong ? Thank you very much
I think you want to use SUM() instead of COUNT().
Because SUM() sums some integers, while COUNT() counts number of occurencies.
And as also stated in the comments, multiple columns with same names will create conflicts, so you have to select the wanted columns explicit (that is usually a good idea anyway).
You could obtain your wanted endgoal by this query:
select
SUM(Number),
t1.Name,
(select val1 FROM t2 WHERE t2.Name = t1.Name LIMIT 1) as val1
FROM t1
GROUP BY t1.Name
Example in sqlfiddle: http://sqlfiddle.com/#!9/04dddf/7
I have table 1 which contains unique values and table 2 which contains multiple values for the same email. What I want to do is select the first value of 'id' - table 2 contains a number of ids and matching emails
SELECT DISTINCT
table1.email,
table2.id FROM
table1
INNER JOIN users ON table1.email = table2.Email
the problem is the output needs to be unique - i.e. one ID - the first one from table2 that is associated with a given email - currently we're getting multiple results - no unique or distinct values.
Probably
any id - add ORDER BY RAND()
1 row of result - add LIMIT 1.
So, the query might be something like this:
SELECT DISTINCT
table1.email,
table2.id
FROM table1
INNER JOIN table2 ON table1.email = table2.email
ORDER BY RAND()
LIMIT 1
Based on new information, it seems like you're looking for something like this instead:
Note: Works on MySQL v8+ and MariaDB 10.2+ that have window function:
SELECT email, id
FROM
(SELECT table1.email,
table2.id,
ROW_NUMBER()
OVER
(PARTITION BY table1.email ORDER BY table2.id) AS 'RowNumber'
FROM table1
INNER JOIN table2 ON table1.email = table2.email) t
WHERE RowNumber=1;
Assign ROW_NUMBER() with table1.email as partition and sort by table2.id ascending (note that the default sorting of ORDER BY is ascending so there's no need to define it as ORDER BY xxx ASC).
Turn the base query into a subquery then do a SELECT .. with condition of WHERE RowNumber=1. Hence, it will return only a single row for each email.
Alternatively, depending on your data, you could just simply do something like this:
SELECT table1.email,
MIN(table2.id) AS minID
FROM table1
INNER JOIN table2 ON table1.email = table2.email
GROUP BY table1.email;
Demo fiddle
I have one join table:
table1_id|table2_id
1|1
1|2
2|1
2|2
3|1
I need to select rows grouped by table2. But I need special grouping. In result row I want to see the following:
table1.id|grouped
1,2|1,2
3|1
I tried different ways.
Select from table1 and group by table2.id. Fail - MySql required query to be grouped my primary table as well.
Select from table2 and group by table1.id and table2.id . Fail - it selects rows from table2 separately, I want them to be concatenated as I shown in the example.
Select from table1 and group by group_concat(table2.id). But MySql does not allow to group by aggregated functions.
My example query: http://sqlfiddle.com/#!9/934b64/4. I need almost the same, but so that it will one row with values:
1,2|1,2
3|1
You are almost there.
You need to use GROUP_CONCAT in SELECT clause, not in GROUP BY clause.
SELECT table1_id,GROUP_CONCAT(table2_id) as grouped
FROM table
GROUP BY table1_id;
See the result in SQL Fiddle
For your requirement, please try the below query:
select t1.id,t1.value,
group_concat(t2.id) as grouped_ids,
group_concat(t2.value) as grouped_values
from table1 t1
join joined_table jt on jt.id1 = t1.id
join table2 t2 on t2.id = jt.id2
group by t1.id,t1.value
Result in SQL Fiddle
An interviewer asked me this question,
You are given two tables with columns as L1,T1 for table1 while T,Name for table2. Write a SQL query to get the desired result.
I'm still stuck on how to write the query to get the desired output.
Used this, SELECT table1.L1, table2.Name FROM table1 INNER JOIN table2 on table1.T1 = table2.T; but this way it won't CONCAT the output for Name wrt L1.
Thanks for helping in advance.
You need an aggegation function as GROUP_CONCAT for obtain the comma separated result for name
SELECT table1.L1,GROUP_CONCAT( table2.Name ORDER BY table2.Name ASC SEPARATOR ',')
FROM table1
INNER JOIN table2 on table1.T1 = table2.T
GROUP BY table1.L1
ORDER BY FIELD(table1.L1,'X','Y','Z')
withou aggegation function you get result on separated rows .. instead with group by an group_concat you obtain all the name related to a one l1 on the same row
You join the two tables using JOIN (Inner Join). Then use GROUP BY to get aggregated data, and then eventually utilize GROUP_CONCAT function to achieve comma separated names. See below:
SELECT table1.l1, GROUP_CONCAT(table2.name)
FROM table1
JOIN table2 ON table1.t1 = table2.t
GROUP BY table1.l1
use this query
SELECT table1.L1, GROUP_CONCAT(table2.name separator ', ')
FROM table1 AS table1
INNER JOIN table2 as table2 ON table1.T1 = table2.t
GROUP BY table1.L1
SQL fiddle here to test it live http://sqlfiddle.com/#!9/3ac3a3/1/0
This sql will get the result.
SELECT L1, GROUP_CONCAT(name) from Table1 INNER JOIN Table2 on T1 = T GROUP BY L1
I don't know if my title is understandable or not, may be someone can help edit my title?
All I want to do is, for example:
I have a table like this
Engineering appears 5 times with different article_category_abbr, and I want to select only one row with the biggest value of num.
Here, it will be Engineering-ENG-192, and Geriatrics&Gerontology will be Geriatrics&Gerontology-CLM-26
But I don't know how to do it on the whole table using mysql
Join your table to a subquery which finds the greatest num value for each sc group.
SELECT t1.*
FROM yourTable t1
INNER JOIN
(
SELECT sc, MAX(num) AS max_num
FROM yourTable
GROUP BY sc
) t2
ON t1.sc = t2.sc AND
t1.num = t2.max_num;
You can have a subquery that gets the largest value for each sc and the resulting rows will then be joined with the table itself based from two columns - sc and num.
SELECT a.*
FROM tableName a
INNER JOIN
(
SELECT sc, MAX(num) AS Num
FROM tableName
GROUP BY sc
) b ON a.sc = b.sc
AND a.num = b.num
Here's a Demo
USE MAX function and GROUP BY like this. Here is more information.
SELECT myID, classTitle, subField, MAX(score) FROM myTable GROUP BY myID, classTitle, subField