Table 1 has columns : entry_id user_id ...
Table 2 has columns : entry_id user_id ...
the user_id entry is not always the same so I would like to extract both of them so I can later on compare them in my script
SELECT * FROM
table1 as t1
INNER JOIN table2 as t2 on t1.entry_id=t2.entry_id
WHERE t1.user_id='%s'
I would like to extract t1.user_id and t2.user_id ...the problem is the result array has only user_id
thank you
Use AS keyword:
SELECT
t1.user_id as t1_user_id
,t2.user_id as t2_user_id
FROM table1 as t1
INNER JOIN table2 as t2
ON t1.entry_id=t2.entry_id
WHERE t1.user_id='%s'
SELECT t1.user_id AS user_id_1, t2.user_id AS user_id2, ...
I think the framework executing the query is at fault for "merging" the two columns here, the result set should have both, but these are stored into an associative array somewhere along the line.
It is a good idea to only request those columns you actually need nonetheless :)
You can effectively use ALIASING (i.e. use the AS keyword).
SELECT t1.user_id as user_id_1, t2.user_id as user_id_2 FROM
table1 as t1
INNER JOIN table2 as t2 on t1.entry_id=t2.entry_id
WHERE t1.user_id='%s'
Related
There is a table where strings are stored by type.
How to write 1 query so that it counts and outputs the number of results of each type.
Tried to do this:
SELECT COUNT(t1.id), COUNT(t2.id)
FROM table t1
LEFT JOIN table t2
ON t2.type='n1'
WHERE t1.type='b2';
But nothing works.
There can be many types, how can this be done?
I think this is what you want:
SELECT t1.type, COUNT(DISTINCT t1.id), COUNT(DISTINCT t2.id)
FROM table1 AS t1
LEFT JOIN table2 AS t2 ON t1.type = t2.type
GROUP BY t1.type
Note that this won't show any types that are only in table2. For that you'd need a FULL OUTER JOIN, which MySQL doesn't have. See How can I do a FULL OUTER JOIN in MySQL? for how to emulate it.
I have two tables from which I need to get data in the same SELECT output. The thing is that I need to limit the amount of results.
Say I have an ID column that is unique in table1, but in table2 it has many rows with that ID.
Now I just want to list how many different IDs I have in table1 and some other information stored in table2.
How can I get the desired output I show in the end?
To make my idea clear I used a "messenger" database for an example.
Tables
T1
Id_thread Date
1 13Dic
2 12Dic
T2
Id_thread Message Name
1 Hi Someone
1 Hi to you Someone
2 Help me? Someother
2 Yes! Someother
Desired output
T1.Id_thread T2.Name T1.Date
1 Someone 13Dic
2 Someother 12Dic
I'd join and use distinct:
SELECT DISTINCT t1.id_thread, t2.name, t1.date
FROM t1
JOIN t2 ON t1.id_thred = t2.id_thread
Use a JOIN and GROUP BY:
SELECT t1.Id_thread, t2.Name, t1.Date
FROM t1
JOIN t2 ON t1.Id_thread = t2.Id_thread
GROUP BY t1.Id_thread
Note that if Name is the same for all rows in t2 that have the same Id_thread, that column probably should be in t1. If you fix that, you don't need the JOIN.
Try this:
SELECT DISTINCT T1.Id_thread, T2.Name, T1.Date
FROM T1
LEFT OUTER JOIN T2 ON T1.Id_thread = T2.Id_thread
select T1.Id_thread,T2.Name,T1.Date from T1
inner join T2 on T1.Id_thread = T2.Id_thread
group by T1.Id_thread
order by T1.Id_thread
You haven't specified how you want the limit the results from Table 2. Considering you just want one row, you can use a CROSS APPLY:
Select T1.Id_thread,T2Table.Name,T1.Date From T1
Cross Apply (Select Top 1 T2.Name From T2 Where T2.Id_thread=T1.Id_thread) T2Table
You can specify other conditions in the inner Select statement if you wish.
I have 2 tables.
How do I know IDs that are in one table and not on the other table? How would I accomplish that?
And then I want to delete all such IDs.
This is pretty simple:
delete from t1
using table1 as t1
left outer join table2 as t2
on t1.id = t2.id
where t2.id is null
It's worth noting that joins are faster than subqueries.
Use this query:
delete from TABLE_A where ID not in (select ID from TABLE_B)
Use this query:
delete from t1
where id not in
(select t2.id from t2)
First a quick explanation: I am actually dealing with four tables and mining data from different places but my problem comes down to this seemingly simple concept and yes I am very new to this...
I have two tables (one and two) that both have ID columns in them. I want to query only the ID columns that are in table two only, not in both. As in..
Select ID
From dbo.one, dbo.two
Where dbo.two != dbo.one
I actually thought this would work but I'm getting odd results. Can anyone help?
SELECT t2.ID
FROM dbo.two t2
WHERE NOT EXISTS(SELECT NULL
FROM dbo.one t1
WHERE t2.ID = t1.ID)
This could also be done with a LEFT JOIN:
SELECT t2.ID
FROM dbo.two t2
LEFT JOIN dbo.one t1
ON t2.ID = t1.ID
WHERE t1.ID IS NULL
Completing the other 2 options after Joe's answer...
SELECT id
FROM dbo.two
EXCEPT
SELECT id
FROM dbo.one
SELECT t2.ID
FROM dbo.two t2
WHERE t2.ID NOT IN (SELECT t1.ID FROM dbo.one t1)
Note: LEFT JOIN will be slower than the other three, which should all give the same plan.
That's because LEFT JOIN is a join followed by a filter, the other 3 are semi-join
I need to make a MySQL query to show data from 3 diferents tables.
This is the table 1:
TABLE1
id
reference
name
email
This is the table 2:
TABLE2:
id
phone
This is the table 3:
TABLE3:
id
phone
I need to show all data from table1, and also the phone from table2 or table3, only if the id in table2 or table3 is the same number that is in the reference field in table1.
Any advice? Thank you!
You can try something like
SELECT t1.*
COALESCE(t2.phone,t3.phone) phone
FROM Table1 t1 LEFT JOIN
Table2 t2 ON t1.reference = t2.id LEFT JOIN
Table3 t3 ON t1.reference = t3.id
Have a look at COALESCE(value,...) and maybe SQL SERVER – Introduction to JOINs – Basic of JOINs
Yes, I have an advice, modify your structure. There's no point in having different tables to hold different phone numbers.
Here's something you can do:
table1( -- you should give it a better name
id,
-- reference, -- not needed now...
name,
email
);
phone_numbers(
id,
table1_id,
phone
);
Now you can do something like:
SELECT table1.*, GROUP_CONCAT(phone)
FROM table1
LEFT JOIN phone_numbers ON table1.id = table1_id
GROUP BY table1.id, name, email -- , whatever fields you have more on table1
You asked for a phone from table2 or from table3.
Because these 2 tables have common columns, we can simplify this whole thing and think about these 2 tables as a single one, by using an UNION clause:
select table1.*, v.phone
from table1
inner join (select * from table2
union
select * from table3) v on v.id = table1.reference
EDIT: corrected table names in the union
SELECT t1.*, t2.*, t3.*
FROM table1 t1 JOIN table2 t2
ON t1.reference = t2.ID
JOIN table3 t3
ON t1.reference = t3.ID
I don't know if you can do CASE statement in select in mysql, but you can try a CASE statement as a column and join. Here is some sudo code.
SELECT t1.*, CASE t2.phone IS NOT t3.phone THEN t3.phone ELSE t2.phone END CASE as PhoneNumber
FROM Table1 t1
LEFT JOIN Table2 t2 ON t1.reference = t2.id
LEFT JOIN Table3 t3 ON t1.reference = t3.id