(SELECT * FROM table1
INNER JOIN table2
ON table1.id = table2.id)
AS t1
JOIN (SELECT ROUND(RAND() * (SELECT MAX(table1.id) FROM table1)) AS id)
AS t2
WHERE t1.id >= t2.id
LIMIT 1)
I try to use RAND() max(id) to get a random mysql result, but get a #1064 error.
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AS t1 JOIN (SELECT ROUND(RAND() * (SELECT MAX(table1.id) FROM table1))' at line 1
Where is the problem? thanks.
(assuming that this code snippet is an entire query)
May be wrong but your statement does not have a SELECT ... in short it looks like this:
t1 JOIN t2 WHERE ...
There is no SELECT something FROM t1 JOIN t2 WHERE ...
Not sure if I make myself clear...
Addendum:
Not sure what you re trying to achieve, but this code bellow returns random IDs from your tables (variation of your query) so perhaps you can use it. A bit messy perhaps but then again I have no idea what are you trying to achieve :).
SELECT * FROM
(SELECT table1.id as id1
FROM table1
INNER JOIN table2
ON table1.id = table2.id) as t1
JOIN (
(SELECT ROUND(RAND() * (SELECT MAX(table1.id) FROM table1)) AS id2)
AS t2 )
WHERE t1.id1 >= t2.id2
LIMIT 1
You can select id1 or id2 instead of *, depending on what is your goal...
(assuming that this code snippet is part of a bigger query)
The problem is this subquery:
(SELECT * FROM table1
INNER JOIN table2
ON table1.id = table2.id)
AS t1
Running it alone:
SELECT * FROM table1
INNER JOIN table2
ON table1.id = table2.id ;
will give no error but it will show/return at least 2 columns with same name (id). This is causing the conflict when you are trying to include it as a subquery in a bigger query.
Related
I have 2 tables, one is table1
and another is table 2
I want the result by a query, like
I have tried select id from table2 order by (select id from table1); but it is giving error.
You can join and sort. But you need a column that defines the ordering of the rows in table1. Let me assume that you have such column, and that is is called ordering_id.
select t2.*
from table2 t2
inner join table1 t1 on t1.id = t2.id
order by t1.ordering_id
You can even use a subquery in the order by clause:
select *
from table2 t2
order by (select t1.ordering_id from table1 t1 where t1.id = t2.id)
Join the two tables and then order the result.But for that you need to have some column for ordering and this does not seems to be the case. Syntax you are using for ordering will not work.
SELECT A.ID, B.NAME FROM TABLE1 A INNER JOIN TABLE2 B
ON(A.ID = B.ID) ORDER BY A.ID DESC
finally got the answer
select t2.*
from table2 t2
inner join table1 t1 on t1.id = t2.id;
I'm trying to JOIN a table with a subquery to limit data to only 1 last row, matching certain values from other FROM or JOINed tables:
SELECT
t1.column1,
t1.column2,
t2.column1,
t3.column2
FROM
table1 t1
JOIN
(
SELECT column1
FROM table2
WHERE t1.column2 > table2.column1
ORDER BY table2.date DESC
LIMIT 1
) t2
JOIN table3 t3 ON t2.column1=t3.column2
Getting an error: Unknown column t1.column2 in 'where clause'. Seems I can't address other columns inside the subquery.
Is what I'm trying to do possible?
If so, what am I doing wrong / what other way could I try this?
In MySQL, implicit and explicit joins together in a single query create the problem. You can not use an implicit JOIN based on a nested SELECT - FROM - WHERE query when there is another explicit JOIN present.
Try below.
SELECT *
FROM table1 t1
INNER JOIN table2 t2 ON t1.column2 > t2.column1
LEFT OUTER JOIN table3 t3 ON t2.column1=t3.column2
You may re-write your query as -
SELECT t1.column1,
t1.column2,
t2.column1,
t3.column2
FROM table1 t1
JOIN (SELECT column1
FROM table2
ORDER BY table2.date DESC
LIMIT 1) t2 ON t1.column2 > t2.column1
JOIN table3 t3 ON t2.column1=t3.column2
The solution for me was:
SELECT
t1.column1,
t1.column2,
t2.column1,
t3.column2
FROM
table1 t1
JOIN table2 t2 ON t2.id =
(
SELECT id
FROM table2
WHERE t1.column2 > table2.column1
ORDER BY table2.date DESC
LIMIT 1
)
JOIN table3 t3 ON t2.column1=t3.column2
More info on:
CROSS/OUTER APPLY in MySQL
https://dba.stackexchange.com/a/170760/13156
I have 2 tables and result as shown in the image below: MySQL DB
What would be best way to join the two tables so we get the result as shown above.
SELECT * FROM (SELECT id, desc FROM table2) as T1
LEFT JOIN (SELECT * FROM table1) as T2 ON T1.id = T2.id
I guess my SQL is not working.
You can use a LEFT JOIN with COALESCE:
SELECT t1.id, COALESCE(t2.desc, t1.desc) AS desc, t1.D1, t1.D2
FROM table1 as T1
LEFT JOIN table2 as T2 ON T1.id = T2.id
Use a left join with coalesce to prioritize table 2's values if they are present, but fallback on table 1's values if not.
select t1.id,
coalesce(t2.desc, t1.desc) as desc,
t1.d1, t1.d2
from table1 t1
left join table2 t2
on t2.id = t1.id
order by t1.id
You can use ifnull:
SELECT t1.id, ifnull(t2.desc, t1.desc) AS desc, t1.D1, t1.D2
FROM table1 as T1
LEFT JOIN table2 as T2 ON T1.id = T2.id
coalesce or case .. when is also possible. All together with the left join
Is is possible to simplify this UNION to avoid the near redundancy of the queries being unioned? As seen here, both queries are similar. They just join on a different column in table2. The reason i use Union, instead of just Inner Joining 2x in the same query is because the results must be in 1 column by virtue of the fact that this queries is used as a subquery.
SELECT t1.id as id
FROM table1 g
INNER JOIN table2 t1 on g.t_id = t1.id
WHERE g.id=1
UNION
SELECT t2.id as id2
FROM table1 g
INNER JOIN table2 t2 on g.t2_id = t2.id
WHERE g.id=1
I don't see why this couldn't be treated as a simple inner join that can be satisfied by a match in either of two predicates. I've removed the original table aliases of t1, t2, and g for the sake of clarity. Since I don't know if the query could produce duplicate rows, I used DISTINCT in order to collapse duplicate rows in the same manner that the UNION did in the original query.
SELECT DISTINCT table2.id
FROM table1
INNER JOIN table2
ON ( table1.t_id = table2.id OR table1.t2_id = table2.id )
WHERE table1.id = 1
;
It is possible to do with two joins, and the IFNULL() function:
SELECT IFNULL (t1.id, t2.id) as id
FROM table1 g
INNER JOIN table2 t1 on g.t_id = t1.id
INNER JOIN table2 t2 on g.t2_id = t2.id
WHERE g.id=1
You might find this simpler:
select distinct t.id
from table2 t
where t.id in (select g.t_id from table1 g) or
t.id in (select g.t2_id from table1 g)
However, the performance would be awful on MySQL. You can also do:
select distinct t.id
from table2 t
where exists (select 1 from table1 g where g.t_id = t.id or g.t2_id = t.id)
The second version should work better in MySQL.
I tried to count how many new tuples are in a subset of t2 as compared to t1 by
SELECT
COUNT(t2.id)
FROM (
(SELECT id, col1 FROM t2 WHERE col2=0 AND col3=0) AS t
LEFT OUTER JOIN
t1
ON
t.id=t1.id
)
WHERE
t1.id IS NULL;
The subset is defined by
(SELECT id, col1 FROM t2 WHERE col2=0 AND col3=0) AS t
But the above program doesn't seem to work, issuing errors.
There is no need to enclose the FROM clause in (). You are referencing t2.id in your aggregate COUNT(), but your SELECT list will only produce t.id from the subquery that encapsulates t2. This version addresses the source of your errors:
SELECT
COUNT(t.id) AS idcount
FROM
(SELECT id, col1 FROM t2 WHERE col2=0 AND col3=0) AS t
LEFT OUTER JOIN t1 ON t.id = t1.id
WHERE t1.id IS NULL
However:
Since your subquery is actually pretty simple, I believe it isn't necessary at all. The whole thing can be done with a LEFT JOIN:
SELECT
/* The equivalent of COUNT(*) in this context */
COUNT(t2.id) AS idcount
FROM
t2
LEFT OUTER JOIN t1 ON t2.id = t1.id
WHERE
t1.id IS NULL
AND (t2.col2 = 0 AND t2.col3 = 0)
are you sure you don't want to do COUNT(t.id)? t2 is in a subquery and is not available to the main query only t and t1 are available.
The problem is the alias. You have:
select count(t2.id)
But, t2 is defined in the subquery, so it is out of scope.
You want:
select count(t.id)