I am having a hard time understanding the limit and offset parts of MYSQL. Could someone use this example "Get the 101st to 200th actor from the actors table. (No need to use any ordering)." and explain to me how this would work and the math behind it? Thanks!
`SELECT * FROM table limit 100, 100` -- get 100 records from row 101 (101 - 200)
This will give you 50 records after 101:
`SELECT * FROM table limit 100, 50` -- get 50 records from row 101 (101 - 150)
For more details, you can see the syntax and usage for limit here.
select actor
from actorTable limit 100, 200
it will get all the actor starting from 101 up to 200 it will always add 1 to the min limit up to the max limit which is 200
Related
I have database with about 500K row in it. I want get random row from row like 1 to 5000 and its limit result limit need like 100.
My current query is like below
'SELECT * FROM user where status='0' LIMIT 10,100'
what should I change or use for get limited random row, so I can get fast result without memory consume ?
Thanks
A database table is an unordered set, so you'll have to provide some order to get 1 to 5000 rows (otherwise those will be any 1 to 5000 rows), may be based on userid.
Once you have that, you can limit the rows in subquery and sort by rand() and get first 100 like this:
select *
from (select
*
from user
where status = 0
order by /* set of columns, may be user_id*/
limit 1, 5000
) t order by rand() limit 100;
This query gives you any 100 random rows from your 5000k rows
select * from user where status='0' order by rand() limit 100
I loaded the result set with top 10 rows as follows.
SELECT * FROM Persons LIMIT 10;
Now how to select next 10 rows.? Like what in google search results can be toggled between search results.
Pardon if question sounds silly because i didn't found any relevant answer on google.
You can give the LIMIT clause a starting point, like this:
SELECT * FROM Persons LIMIT 50, 10;
This would mean the offset is 50 (it skips the first 50 rows), and the next 10 rows are selected. See also in the manual: MySQL SELECT Syntax.
Use OFFSET + LIMIT to do this
SELECT * FROM Persons
ORDER BY somecol
OFFSET 10 LIMIT 10 -- LIMIT 10 OFFSET 10
For Mysql
SELECT * FROM Persons
ORDER BY somecol
LIMIT 10 OFFSET 10 --LIMIT 10,10
Note: Make sure you add Order by to get meaningful results
Write a SQL Query for finding 98th or 99th element from given 100 numbers.
Just use offset and limit. For the 99th number:
select n
from numbers
order by n
limit 98, 1;
SELECT * FROM `daily_report` limit 97,2
this will give you two records of 98 and 99
Here is my query, which i am using for pagination
SELECT DISTINCT email_list.*, email_counter.phone as e_phone,email_counter.email as e_email,email_counter.marketing as e_marketing
FROM Data_TLS_builders as email_list
LEFT JOIN wp_pato_email_list_counters as email_counter on email_counter.email_id = email_list.URN
LIMIT 120 OFFSET 150
Rather than starting at 120 and finishing at 150, which should display 30 results, mysql is returning 120 results and ignoring the OFFSET. I have tried LIMIT 120,150 and still the same?
Any idea how to solve?
SELECT DISTINCT email_list.*, email_counter.phone as e_phone,email_counter.email as e_email,email_counter.marketing as e_marketing FROM Data_TLS_builders as email_list LEFT JOIN wp_pato_email_list_counters as email_counter on email_counter.email_id = email_list.URN LIMIT 30 OFFSET 120
Limit specifies number of records.
OFFSET specifies upto how many records it should skip.
The above query returns 30 records from 121.
You have to switch the limit parameters.
Solution 1:
SELECT DISTINCT email_list.*, email_counter.phone as e_phone,email_counter.email as e_email,email_counter.marketing as e_marketing FROM Data_TLS_builders as email_list LEFT JOIN wp_pato_email_list_counters as email_counter on email_counter.email_id = email_list.URN LIMIT 30 OFFSET 120
Solution 2:
SELECT DISTINCT email_list.*, email_counter.phone as e_phone,email_counter.email as e_email,email_counter.marketing as e_marketing FROM Data_TLS_builders as email_list LEFT JOIN wp_pato_email_list_counters as email_counter on email_counter.email_id = email_list.URN LIMIT 120, 30
You can also have a look into the documentation: http://www.w3schools.com/php/php_mysql_select_limit.asp.
LIMIT will tell mysql HOW MANY results you want to show.
OFFSET will tell mysql where to START.
if you want to display 30 results starting at 120, it should be:
LIMIT 30 OFFSET 120
or
LIMIT 120, 30
I want to iterate through records returned from a MySQL database using Perl, but only ten records at a time. The reason is that the server component can only handle 10 items per request.
For example:
If the query returned 35 records then
I have to send the data in 4 requests:
Request # # of Records
-------- --------
1 10
2 10
3 10
4 5
What is the best way to accomplish the task?
Look at the LIMIT clause for MySQL. You could have a query like:
SELECT * from some_table LIMIT 0, 10;
SELECT * from some_table LIMIT 10, 10;
etc. where the first number after LIMIT is the offset, and the second number is the number of records.
You'd of course first need to do a query for the total count and figure out how many times you'll need to run your select query to get all results.
Alternatively, in Perl you can use an ORM package like DBIx::Class that can handle pagination through sets of results and auto-retrieving them for you.
You can adjust the query to select 10 rows:
select *
from yourtable
order by idcolumn
limit 10;
When iterating over the rows, store the ID of the row you process. After you've processed 10 rows, fetch the next 10:
select *
from yourtable
where idcolumn > stored_id
order by idcolumn
limit 10;
Continue the last query until it returns less than 10 rows.
For first page:
SELECT *
FROM table1
ORDER BY
field
LIMIT 0, 10
For seconds page:
SELECT *
FROM table1
ORDER BY
field
LIMIT 10, 10
etc.