Hello everybody
Well my question is about sql commands...
If I have 2 tables with the same number of columns and the same fieldnames (e.g: A(n,name,date) and B(n,name,date))
In the website, I want to retrieve data from both tables and display them in order by date descendent.
(The use of two tables is due to difference in tables database or server,or just the use of every table.. sometimes there's a need to display both tables in one order)
exemple
table Sport_news(N_event,Title,Texte,Date)
table International_news(N_event,Title,Texte,Date)
Display:
Christiano Ronaldo ... 2011/25/01
christiano ronaldo is one of the famous...
Barack Obama president of the USA... 2011/24/01
Barak obama........
The arsenal has... 2011/23/01
Chamakh, player of arsenal is anger.....
I hope that the idea is clear : and thank you!
You want UNION
select a.name,a.date
from table1 a
where ...
UNION ALL
select b.name,b.date
from table2 b
where ...
order by 2 desc
When you use a UNION, you specify the order by with column numbers instead of names.
Related
I have a simple table
**targeted_url_redirect targeted_countries msg_type non_targeted_url**
http://new.botweet.com india,nepal,philippines NEW http://twisend.com
http://expapers.com United States,Canada OLD http://all.twisend.com
https://tweeasy.com india,england OLD http://all.twisend.com
I receive traffics on my website followerise.com and I want to redirect users to specific urls based on their countries as defined in the above table. I am able to write query to get rows for the users who coming from the countries that are target stored in my database. But I am looking for a solution to get all the rows if the targeted_countries condition not return any rows.
I written below queries.
SELECT * FROM tweeasy_website_redirection
WHERE message_type='OLD'
AND targeted_countries LIKE '%#country%'
This query gives me desired rows if visitor coming from the countries india,england,United States,Canada
But I want all rows (2nd and 3rd) should be fetched if a user coming from the countries not specified in targeted_countries column.
Also let me know if I need to restructure this table into 2 or more tables to get desired result.
One option uses not exists:
SELECT t.*
FROM tweeasy_website_redirection t
WHERE
t.message_type = 'OLD'
AND (
t.targeted_countries LIKE '%#country%'
OR NOT EXISTS (
SELECT 1
FROM tweeasy_website_redirection t1
WHERE t1.targeted_countries LIKE '%#country%'
)
)
When it comes to the structure of your table: one design flaw is to store list of values as CSV list. You should have two separate tables: one to store the urls, and the other to store the 1-N relationship between urls and countries. Something like:
table "url"
id targeted_url_redirect msg_type non_targeted_url
1 http://new.botweet.com NEW http://twisend.com
2 http://expapers.com OLD http://all.twisend.com
3 https://tweeasy.com OLD http://all.twisend.com
table "url_countries"
url_id country
1 india
1 nepal
1 philippines
2 united states
2 canada
3 india
3 england
select * from tweeasy_website_redirection
where targeted_countries not in (SELECT targeted_countries FROM stack WHERE targeted_countries LIKE '%#country%')
Here is a table
id date name
1 180101 josh
2 180101 peter
3 180101 julia
4 180102 robert
5 180103 patrick
6 180104 josh
7 180104 adam
I need to get all the names whom having the same days as 'josh'. how can i achieve it without groupping the whole table together. i need to keep it efficient (this is not my real table, i just simplified my problem here, and i have hundred thousands of records, and 99% of the rows have different dates, so groupable rows by date is kind of rare).
So basicaly what i want is: if 'josh' is the target, i need to get 'josh,peter,julia,adam' (actually the first 10 distinct names sharing the same date with josh).
SELECT
COUNT(date) as datecount,
GROUP_CONCAT(DISTINCT name) as names,
FROM
table
GROUP BY
date
HAVING
datecount>1
// && name IN ('josh') would work nice for me, but im getting error because 'name' is not in GROUPED BY
LIMIT 10
Any idea ? As i mentioned it needs to be fast, and most of the rows have unique dates
Join the table with itself on date:
select distinct t1.name
from tbl t1
join tbl t2 using (date)
where t2.name = 'josh'
Demo
For the best performance you would have indexes on (name) and (date, name).
SELECT column_1 FROM table_1,table_2;
When I ran this on my database it returned huge number of rows with duplicate column_1 values. I could not understand why I got these results. Please explain what this query does.
it gives you a cross product from table 1 and table 2
In more layman's terms, it means that for each record in Table A, you get every record from Table B (all possible combinations).
TableA with 3 records and Table B with 3 records gives 9 total records in the result:
TableA-1/B-1
TableA-1/B-2
TableA-1/B-3
TableA-2/B-1
TableA-2/B-2
TableA-2/B-3
TableA-3/B-1
TableA-3/B-2
TableA-3/B-3
Often used as a basis for Cartesian Queries (which themselves are the means to generate, say, a list of future dates based on a recurrence schedule: give me all possible results for the next 6 months, then restrict that set to those whose factor matches my day of the week)
This is 'valid' way of cross joining two tables; it is not the preferred way though. Cross Join would be much clearer. An on condition would then be helpful to limit results,
Imagine that i have 3 friends named Jhon, Ana, Nick; then i have in the other table 2 are T-shirts a red and a yellow and i wanna know witch is from.
So in the query being tableA:Friends and tableB:Tshirts returns:
1|JHON | t-shirt_YELLOW
2|JHON | t-shirt_RED
3|ANA | t-shirt_YELLOW
4|ANA | t-shirt_RED
5|NICK | t-shirt_YELLOW
6|NICK | t-shirt_RED
As you see this join has no relational logic between friends and Tshirts so by evaluating all the posible combination generates what you call duplicates.
I have a single table that uses test# as the primary key. Here is what that table looks like:
Test# Name VerbalScore readingScore Notes
1 Bobby 92 Good job
2 Bobby 40 You Suck Bobby
The problem is I want to view and be able to see when there are multiple verbal scores for the same Name (so be able to see if the person took the same test more than once).
I want to have some kind of select statement to get this result from the above table:
1 Bobby 92 40 Good job, You Suck Bobby
Is that possible?
I am not totally sure I understand what you mean by "see when there are multiple verbal scores" but with mysql 5+, try
SELECT
Name,
GROUP_CONCAT(VerbalScore),
GROUP_CONCAT(readingScore),
GROUP_CONCAT(Notes)
FROM
myTable
GROUP BY
Name;
GROUP_CONCAT is a mysql specific grouping function.
So, I have a table with 3 columns, of which the first column consists of IDs and the last column consists of dates. What I need is, to sort the table by dates, and remove any duplicate IDs with a later date (and keep the ID with the earliest date).
For example,
This is how my table originally looks like -
123 Ryan 01/01/2011
345 Carl 03/01/2011
123 Lisa 01/02/2012
870 Tiya 06/03/2012
345 Carl 07/01/2012
I want my resultant table to look like this -
123 Ryan 01/01/2011
345 Carl 03/01/2011
870 Tiya 06/03/2012
I'm using VBA Access Code to find a solution for the above, and used SQL Queries too, however my resultant table either has no duplicates whatsoever or displays all the records.
Any help will be appreciated.
This will create a new table:
SELECT tbl.SName, a.ID, a.BDate
INTO NoDups
FROM tbl
INNER JOIN (
SELECT ID, Min(ADate) As BDate
FROM tbl GROUP BY ID) AS a
ON (tbl.ADate = a.BDate) AND (tbl.ID = a.ID);