Is there a way to tell MySQL that while making something like this
SELECT id, MAX(seq) FROM t1 GROUP BY ident;
I can also get the id value? I know I shouldn't be using id if it's not in a group by but I feel like its strange to make a multi pass to get the row ids with the maximum seq field when it already passed it. So what is the most effective way to do this? id is the primary key
SELECT a.*
FROM tableName
INNER JOIN
(
SELECT ident, MAX(seq) seq
FROM tableName
GROUP BY ident
) b ON a.ident = b.ident AND
a.seq = b.seq
Mabye:
SELECT MAX(a.seq), (SELECT id FROM t1 as b where b.ident=a.ident AND MAX(a.seq) = b.seq LIMIT 1) as id FROM t1 AS a GROUP BY a.ident;
Fiddle
Try using self-join:
SELECT t1.* FROM MyTable t1
JOIN
(SELECT ident, MAX(seq) AS MAX_Seq
FROM MyTable
GROUP BY ident
) t2
ON t1.seq = t2.MAX_Seq
AND t1.ident = t2.ident
See this sample SQLFiddle
What is seq exactly ?
I guess you can also order your results ?
SELECT id FROM t1 GROUP BY ident ORDER BY seq DESC
Regarding to the others answer, seq is in another table ?
Related
Consider the following table:
As shown in image, I want to return all the data from only first distinct id. How can I achieve that in MySQL ?
You can filter with a subquery. Assuming that by first you mean the row with the earlier start_time, that would be:
select t.*
from mytable t
where t.start_time = (
select min(t1.start_time) from mytable t1 where t1.call_unique_id = t.call_unique_id
)
from your_table t1
join
(
select min(call_unique_id) as id
from your_table
group by start_time
) t2 on t1.id = t2.id
group by should also do the job. so try
select * from your_table group by call_unique_id
I am Using the below table
The case_id for two rows. If the case Id is same then I would want to fetch the row that has Test_script_type as automation and ignore the manual. How can I achieve it with a SQL query..If there is only manual fetch the manual row. How can I achieve it with a SQL query. The Output would be like :
Help is appreciated. Thanks for your time In-advance
You could adress this with not exists:
select t.*
from mytable t
where
script_type = 'Automation'
or not exists (
select 1
from mytable t1
where
t1.case_id = t.case_id
and t1.script_name <> t.script_name
and t1.script_type = 'Automation'
)
You can also filter with a correlated subquery:
select t.*
from mytable t
where t.script_type = (
select min(t1.script_type) -- This gives priority to 'Automation' against 'Manual'
from mytable t1
where t1.case_id = t.case_id
)
SELECT t1.*
FROM `table` t1
LEFT JOIN `table` t2 ON t1.case_id = t2.case_id AND t1.script_type != t2.script_type
WHERE t1.script_type = 'automation' OR t2.case_id IS NULL
You could do something like the following:
WITH cte AS (
SELECT T1.CASE_ID, T1.SCRIPT_NAME, T1.SCRIPT_TYPE,
COUNT(T1.CASE_ID) OVER (PARTITION BY T1.CASE_ID) AS cnt
FROM table1 T1
)
SELECT cte.CASE_ID, cte.SCRIPT_NAME, cte.SCRIPT_TYPE
FROM cte
WHERE (cte.cnt > 1 AND UPPER(cte.SCRIPT_TYPE) = UPPER('AUTOMATION'))
OR cte.cnt = 1
The WITH statement adds a column counting how many times the case_id value is duplicated, which helps identify the rows you want to work with.
Here is an example of it working with the data you have provided: SQLFiddle
If you are using MSSQL Server, You may try below query -
SELECT *
FROM (SELECT CASE_ID, SCRIPT_NAME, SCRIPT_TYPE, ROW_NUMBER() OVER(PARTITION BY CASE_ID ORDER BY SCRIPT_TYPE) RN
FROM YOUR_TAB) T
WHERE RN = 1
I have the above mentioned tables in my database. I first receive a COURSE variable from my previous PHP page. I need to print the list of student names along with their student_Ids who haven't taken the course. For the tables above, if the variable I receive is A, then I need to print Jake along with his student_id. As Jake's student id 3, is not associaetd with Course A.
I tried following query, which doesn't seem to work and I'm unsure where I'm wrong
SELECT DISTINCT T1.name, T1.student_id
FROM Table 1 T1, Table 2 T2
WHERE T1.student_id = T2.student_id AND
T2.COURSE != :variable
ORDER BY T1.name ASC,
T1.student_id ASC
variable : A
I appreciate that this must seem very old-fashioned, but then again, so am I...
SELECT DISTINCT x.*
FROM t1 x
LEFT
JOIN t2 y
ON y.student_id = x.student_id
AND y.course = 'a'
WHERE y.student_id IS NULL;
There are lots of options. For instance, you could use a subquery:
SELECT name, student_id FROM t1 WHERE student_id NOT IN (SELECT student_id FROM t2 WHERE course='A')
You can use NOT EXISTS to find a list of students who have not taken the course:
SELECT * FROM T1
WHERE NOT EXISTS (
SELECT * FROM T2
WHERE T1.StudentId = T2.StudentId
AND T2.Course = :variable
)
ORDER BY name ASC, student_id
the sql as follows come from mysql document. it is:
SELECT * FROM t1 AS t
WHERE 2 = (SELECT COUNT(*) FROM t1 WHERE t1.id = t.id);
The document say It finds all rows in table t1 containing a value that occurs twice in a given column , and doesnot explain the sql.
t1 and t is the same table, so the
count(*) in subquery == select count(*) from t
, isn't it?
count(*) in subquery == select count(*) from t
is wrong. because in mysql you can't use it like that. so you have to run it like that to get result of same id having two rows.
if you want to get count of same occurrence,
SELECT id, name, count(*) AS all_count FROM t1 GROUP BY id HAVING all_count > 1 ORDER BY all_count DESC
And also you can get values as your query like this as well,
select * from t1 where id in ( select id from t1 group by id having count(*) > 1 )
The query contains a correlated subquery in WHERE clause:
SELECT COUNT(*) FROM t1 WHERE t1.id = t.id
It is called correlated because it is related to the main query via t.id. So, this subquery counts the number of records having an id value that is equal to the current id value of the record returned by the main query.
Thus, predicate
(SELECT COUNT(*) FROM t1 WHERE t1.id = t.id) = 2
evaluates to true for any row with an id value that occurs twice in the table.
SELECT * FROM t1 AS t
WHERE 2 = (SELECT COUNT(*) FROM t1 WHERE t1.id = t.id);
This query goes through each record in t1 and then in the subquery looks into t1 again to see if in this case id is found 2 times (and only 2 times). You can do the same for any other column in t1 (or any table for that matter).
When you would like to see all values that are multiple times in the table, change WHERE 2 = by WHERE 1 <. This will also give you the values that are 3 times, 4 times, etc. in the table.
{
SELECT id,count( * )
FROM
MyTable
group by id
having count( * )>1
}
with this code, you can see the rows which repet more than one,
and you can change this query by yourself
How about using GROUP BY and HAVING:
SELECT id, count(1) as Total FROM MyTable AS t1
GROUP BY t1.id
HAVING Total = 2
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