I have only one table with the name of offers and it has multiple offers in it like each time we pull in an offer, we create a new row for example: for travelling to Timbuktu, there can be 10 or more rows each containing an offer, each time a offers comes in, it is being saved with PHP unix timestamp in the column name 'created_on', so to figure out which offer is latest, I am currently using following query:
SELECT * FROM offers WHERE city= 'Timbuktu' AND created_on=(SELECT max(created_on)from offers WHERE city = 'Timbuktu')
This serves the purpose if I have to fetch only one latest row, if say I want to fetch last 4 or 8 rows with the greatest timestamp, how I can do that in most efficient way?
SELECT *
FROM offers
WHERE city= 'Timbuktu'
order by created_on desc
limit 0, 8
and for 1 row you can use same request just replace 8 with 1
SELECT * FROM offers WHERE city='Timbuktu' ORDER BY created_on DESC LIMIT 4;
Related
I will explain the logic:
I need to retrieve only the most recent room type/rate plan combinations from the rateplan_roomtypeTable.
room type ID and rate plan id are located in separate columns
there are 2 conditions that need to be met: all active room type/rate plan combinations need to be retrieved along with all room type/rate plan combinations that have produced even if they are not active. All these combinations need to be the most recent ones.
The desired results would be like the table I ll share with you:
Your help with the below query will be much appreciated:
select
Id
, RoomTypeId
, RateTypeId
,isactiveRateType
,isactiveRoomType
, RatePlanName
, RoomTypeName
FROM
rateplan_roomtypeTable
where
RateTypeId IN (select RateTypeId from ProductionTable where (cast(bookingdate as date) between date_add('day',-92, current_date) and date_add('day', -2, current_date)))
OR (isactiveRateType = 1 and isactiveRoomType = 1)
GROUP BY
1,2,3,4,5
Thank you
How to go about selecting all data from the most recent three records in table. This is specifically for a blog that on the home page will show the three most recently dated articles.
ID |title |date |...
---------------------------
1 |exampTitle1|2018-04-25|
2 |exampTitle2|2019-02-10|
3 |exampTitle3|2007-12-21|
4 |exampTitle4|2019-08-10|
The example table shows a subsection of the table, I need to select all data from each record but only from the most recent THREE records, I am aware of MAX() but as far as I am aware that can only get the most recent, not
In SQL, you can order the rows with ORDER BY. Then, you can LIMIT what you are selecting with the LIMIT 3 spesific to SQL of some DBMS products such as MySQL :
SELECT * FROM table ORDER BY date DESC LIMIT 3;
This should work, by sorting by ID in descending order and using LIMIT:
SELECT * FROM <TABLE_NAME> ORDER BY id DESC LIMIT 3
I'm looking for a mysql select that will allow me to select (LIMIT 8) records after some changing number of first few matches;
select id
from customers
where name LIKE "John%"
Limit 8
So if i have a table with 1000 of johns with various last names
I want to be able to select records 500-508
You can send the offset to the limit statement, like this:
SELECT id
FROM customers
WHERE name LIKE "John%"
LIMIT 8 OFFSET 500
Notice the OFFSET 500 on the limit. That sets the 'start point' past the first 500 entries (at entry #501).
Therefor, entries #501, #502, #503, #504, #505, #506, #507 and #508 will be selected.
This can also be written:
LIMIT 500, 8
Personally, I don't like that as much and don't understand the order.
Pedantic point: 500-508 is 9 entries, so I had to adjust.
As a solution please try executing the following sql query
select id from customers where name LIKE "John%" Limit 500,8
I need to show some records sorted based on modified column (latest activity on top)
(Post with new edit or comments at the top)
App UI has twitter like 'more' post button for infinite scroll. each 'more' will add next 10 records to UI.
Issue is that pagination index breaks when any of the to be shown record is modified
for example
Suppose i have records A,B,C,..Z in jobs table.
first time I'm' showing the records A-J to the user using
SELECT * FROM Jobs WHERE 1 ORDER BY last_modified DESC LIMIT 0, 10
second time if none of the records are modified
SELECT * FROM Jobs WHERE 1 ORDER BY last_modified DESC LIMIT 10, 10
will return K-T
But if some body modifies any records after J before the user clicks 'more button',
SELECT * FROM Jobs WHERE 1 ORDER BY last_modified DESC LIMIT 10, 10
will return J-S
Here record J is duplicated. I can hide it by not inserting J to the UI, but the more button will show only 9 records. But this mechanism fails when large number of records are updated, If 10 records are modified, the query will return A-J again.
What is the best way to handle this pagination issue?
Keeping a second time stamp fails if a record has multiple updates.
Server cache of queries?
I would do a NOT IN() and a LIMIT instead of just a straight LIMIT with a pre-set offset.
SELECT * FROM Jobs WHERE name NOT IN('A','B','C','D','E','F','G','H','I','J')
ORDER BY last_modified DESC LIMIT 10
This way you still get the most recent 10 every time but you would need to be tracking what IDs have already been shown and constantly negative match on those in your sql query.
Twitter timelines not paged queries they are queried by ids
This page will help you a lot understanding timeline basics https://dev.twitter.com/docs/working-with-timelines
lets say each column have id field too
id msg
1 A
2 B
....
First query will give you 10 post and max post_id will be 10
Next query should be
SELECT * FROM Jobs WHERE id > 10 ORDER BY last_modified DESC LIMIT 0, 10
I don't know the exact solution but I can give it a try.
First u need an integer ID column in your Job table.
Now send a max_id = null along with limit = 10 and offset = 0 from UI.
In this case if max_id is null, set max_id to (MAX(ID) + 1) of Table.
SELECT (MAX(ID) + 1) INTO max_id FROM Jobs;
Later find the records:
SELECT * FROM Jobs WHERE ID < max_id ORDER BY last_modified DESC LIMIT 10 OFFSET 0;
Return the records to UI.
Now from UI set max_id = ID of first record in the response array, offset = offset + limit.
Now onwards try with updated values of max_id and offset:
SELECT * FROM Jobs WHERE ID < max_id ORDER BY last_modified DESC LIMIT 10 OFFSET 10;
I wonder if anyone could help with a MySQL query I am trying to write to return relevant results.
I have a big table of change log data, and I want to retrieve a number of record 'groups'. For example, in this case a group would be where two or more records are entered with the same timestamp.
Here is a sample table.
==============================================
ID DATA TIMESTAMP
==============================================
1 Some text 1379000000
2 Something 1379011111
3 More data 1379011111
3 Interesting data 1379022222
3 Fascinating text 1379033333
If I wanted the first two grouped sets, I could use LIMIT 0,2 but this would miss the third record. The ideal query would return three rows (as two rows have the same timestamp).
==============================================
ID DATA TIMESTAMP
==============================================
1 Some text 1379000000
2 Something 1379011111
3 More data 1379011111
Currently I've been using PHP to process the entire table, which mostly works, but for a table of 1000+ records, this is not very efficient on memory usage!
Many thanks in advance for any help you can give...
Get the timestamps for the filtering using a join. For instance, the following would make sure that the second timestamp is in a completed group:
select t.*
from t join
(select timestamp
from t
order by timestamp
limit 2
) tt
on t.timestamp = tt.timestamp;
The following would get the first three groups, no matter what their size:
select t.*
from t join
(select distinct timestamp
from t
order by timestamp
limit 3
) tt
on t.timestamp = tt.timestamp;