I have a contents table and the entires in it are as shown in the attached figure
There are more than 100,000 entries. I want to fetch the data where the update_date for commit=0 is greater than update_date for commit=1. I also need the corresponding row for commit=1.
I tried a few things, but takes a long time to retrieve the results. What is the best SQL query I can use. I am using MySQL database.
EDIT
I have now updated the table. There is an attribute called content_id which binds the rows together.
A query like this gives me half of what I want
select a.* from contents a, contents b where
a.content_id=b.content_id and
a.update_date > b.update_date and
a.committed=0 and b.committed=1
I also want the corresponding entries from committed=1, but they should be appended at the bottom as rows and not vertically concatenated as columns.
For example, I cannot use
select * from contents a, contents b where
a.content_id=b.content_id and
a.update_date > b.update_date and
a.committed=0 and b.committed=1
because the results from 'b' are appended vertically. Also, is there a better way to write this query. This works really slow if there are many entries in the database.
I am assuming that in the above example, you only need id=2 as for content id = 1, the update_date for commit=0 is greater than update_date for commit=1 and in that case you need data for commited = 1.
I an using Oracle, so you need to find a suitable replacement for row_number() funtion in mysql.
The logic would be
Create a view on the existing table to use rownumber so it will give rownumber like below order by time desc (see if you use a nested query to do it)
ID, CONTENT_ID, COMMITED, UPDATE_DATE, ROWN
2 1 1 06-SEP-15 00:00:56 1
1 1 0 07-SEP-15 00:00:56 2
3 2 0 03-SEP-15 00:00:56 1
4 2 1 04-SEP-15 00:00:56 2
Now select only rows where where rown=1 and commited=1
This is the query in oracle. The second with query c2 will be your view.
Oracle query
with c1 (id, content_id,commited,update_date) as
(
select 1,1,0,sysdate from dual union
select 2,1,1,sysdate-1 from dual union
select 3,2,0,sysdate-4 from dual union
select 4,2,1,sysdate-3 from dual
),
c2 as
(select c1.*,row_number() over(partition by content_id order by update_date) as rown from c1)
select id,content_id,commited,update_date from c2
where rown=1 and commited=1
ID, CONTENT_ID, COMMITED, UPDATE_DATE, ROWN
Output
ID, CONTENT_ID, COMMITED, UPDATE_DATE
2 1 1 06-SEP-15 00:06:17
Related
Table Data:
ID
Type
1
A
2
A
3
B
4
A
5
A
6
B
7
B
8
A
9
A
10
A
How to get only rows with IDs 1,3,4,6,8, or the first records on type-change by single query?
We were doing this in code using multiple queries and extensive processing especially for large data, is there a way to do this in a single query?
Use LAG() window function to get for every row the previous row's type and compare it to the current type.
Create a flag column that is true if the 2 types are different and use it to filter the table:
WITH cte AS (
SELECT *, type <> LAG(type, 1, '') OVER (ORDER BY id) flag
FROM tablename
)
SELECT * FROM cte WHERE flag;
I assume that the column type does not contain empty values (nulls or
empty strings).
See the demo.
When I use in keyword in sql, there may be some id is missing , but I want treat them like they exist and other columns are null or 0.
For example, suppose I have a table with two columns and some rows:
[id,value1]
1 1
2 4
3 3
5 5
I may write sql like this:
select * from table where id in (1,4,5) order by value1 limit 0,2 ;
When this sql is executed, the return result is [(1,1),(5,5)].
But what I want is [(4,0),(1,1)], because I want to treat the missing id 4 like it exists in the table.
So the question is : Is there some elegant way to achieve it using sql instead of select all rows and sort them in memory.
Use a left join:
select *
from (select 1 as id union all
select 4 union all
select 5
) i left join
table t
using (id)
order by t.value1
limit 0, 2 ;
Note that you are ordering by a value in the existing table, so this depends on the fact that NULL is ordered before other values.
I got table in db in following way:
id Name Type
1. Aero. Product
2. Ddd. Product
3. Sass. Image
4. Rrrrr. Image
This is just to understand and actual table in much bigger scale.
So the question is how to get diversfied results so the product type wont be like product,product, image, image
If i will do select * from table where 1 order by ‘id’
Results having grouped “type”
I want have results like
1 blabla product
3 blabla image
2 blabla product
4 blabla image
So the records with same type will be spreaded over results and
As much as possible wont stay together
As already suggested its better if you do this type of sorting in your application code, In Mysql you can do this by using user defined variables.
First break your data according to your types, get data for products and assign a row number and do the same with second data set for type image and then merge these sets using union operation and then sort them by row number
select *
from(
select d1.*, #row1:= #row1 + 1 as row
from demo d1,
(select #row1:=0) t1
where `Type` = 'Product'
union all
select d2.*, #row2:= #row2 + 1 as row
from demo d2,
(select #row2:=0) t2
where `Type` = 'Image'
) t
order by t.row, t.Type desc
demo
I'm working on improving some queries I inherited, and was curious if it was possible to do the following - given a table the_table that looks like this:
id uri
---+-------------------------
1 /foo/bar/x
1 /foo/bar/y
1 /foo/boo
2 /alpha/beta/carotine
2 /alpha/delic/ipa
3 /plastik/man/spastik
3 /plastik/man/krakpot
3 /plastik/man/helikopter
As an implicit intermediate step I'd like to group these by the 1st + 2nd tuple of uri. The results of that step would look like:
id base
---+---------------
1 /foo/bar
1 /foo/boo
2 /alpha/beta
2 /alpha/delic
3 /plastik/man
And the final result would reflect the number of unique tuple1 + tuple2 values, per unique id:
id cnt
---+-----
1 2
2 2
3 1
I can achieve these results, but not without doing a subquery (to get the results of the implicit step mentioned above), and then select/grouping out of that. Something like:
SELECT
id,
count(base) cnt
FROM (
SELECT
id,
substring_index(uri, '/', 3) AS base
FROM the_table
GROUP BY id, base
)
GROUP BY id;
My reason for wanting to avoid the subquery is that I'm working with a fairly large (20M rows) data set, and the subquery gets very expensive. Gut tells me it's not doable, but figured I'd ask SO...
There's no need for a subquery -- you can use count with distinct to achieve the same result:
SELECT
id,
count(distinct substring_index(uri, '/', 3)) AS base
FROM the_table
GROUP BY id
SQL Fiddle Demo
BTW -- this returns count of 1 for id 3 -- I assume that was a typo in your posting.
Got this:
Table a
ID RelatedBs
1 NULL
2 NULL
Table b
AID ID
1 1
1 2
1 3
2 4
2 5
2 6
Need Table a to have a comma separated list as given in table b. And then table b will become obsolete:
Table a
ID RelatedBs
1 1,2,3
2 4,5,6
This does not rund through all records, but just ad one 'b' to 'table a'
UPDATE a, b
SET relatedbs = CONCAT(relatedbs,',',b.id)
WHERE a.id = b.aid
UPDATE: Thanks, 3 correct answers (marked oldest as answer)! GROUP_CONCAT is the one to use. No need to insert commas between the ids using relatedids = CONCAT(relatedids,',',next_id) that is done automatic by GROUP_CONCAT.
You'll have to use the mysql group_concat function in order to achieve this: http://dev.mysql.com/doc/refman/5.1/en/group-by-functions.html#function_group-concat
Look into GROUP_CONCAT(expr)
mysql> SELECT student_name,
-> GROUP_CONCAT(DISTINCT test_score
-> ORDER BY test_score DESC SEPARATOR " ")
-> FROM student
-> GROUP BY student_name;
You can't do that in standard SQL. You could write a stored procedure to do that. I had a similar problem, but I was using PostgreSQL so I was able to resolve it by writing a custom aggregate function so that you can do queries like
select aid, concat(id)
from b group by
aid
Update: MySQL has a group_concat aggregate function so you can do something like
SELECT id,GROUP_CONCAT(client_id) FROM services WHERE id = 3 GROUP BY id
as outlined here.