Have a table where certain rows come in couples which have a matching GUID. Just wondering how to SELECT all data from the table but ONLY if the rows exist as a couple with a matching GUID.
You can use a query like this:
SELECT *
FROM yourtable
WHERE GUID IN (SELECT GUID FROM yourtable GROUP BY GUID HAVING COUNT(*)=2)
The subquery will return all GUIDs that appears exactly twice, the outer query will return all rows associated to those GUIDs.
Please see fiddle here.
Try something like this:
SELECT t1.*
FROM
table t1
, table t2
WHERE
t1.guid = t2.guid
AND t1.id <> t2.id
;
table: your table name
id: some field that you know is different for both rows
Try
SELECT t.*
FROM Table1 t JOIN
(
SELECT guid
FROM Table1
GROUP BY guid
HAVING COUNT(*) = 2
) q ON t.guid = q.guid
Here is SQLFiddle demo
Related
I have 2 sql table as follows:
First table t1:
Second table t2:
I need to calculate the count of "Number" column based on "Name" column from t1 and merge it with t2.
I wrote following code. But it seems not working
select *
from (
select Name, count(Number) as count
from t1
group by Name ) as a
join ( select *
from t2 ) as b
on a.Name = b.Name;
Can any one figure out what is wrong ? Thank you very much
I think you want to use SUM() instead of COUNT().
Because SUM() sums some integers, while COUNT() counts number of occurencies.
And as also stated in the comments, multiple columns with same names will create conflicts, so you have to select the wanted columns explicit (that is usually a good idea anyway).
You could obtain your wanted endgoal by this query:
select
SUM(Number),
t1.Name,
(select val1 FROM t2 WHERE t2.Name = t1.Name LIMIT 1) as val1
FROM t1
GROUP BY t1.Name
Example in sqlfiddle: http://sqlfiddle.com/#!9/04dddf/7
the sql as follows come from mysql document. it is:
SELECT * FROM t1 AS t
WHERE 2 = (SELECT COUNT(*) FROM t1 WHERE t1.id = t.id);
The document say It finds all rows in table t1 containing a value that occurs twice in a given column , and doesnot explain the sql.
t1 and t is the same table, so the
count(*) in subquery == select count(*) from t
, isn't it?
count(*) in subquery == select count(*) from t
is wrong. because in mysql you can't use it like that. so you have to run it like that to get result of same id having two rows.
if you want to get count of same occurrence,
SELECT id, name, count(*) AS all_count FROM t1 GROUP BY id HAVING all_count > 1 ORDER BY all_count DESC
And also you can get values as your query like this as well,
select * from t1 where id in ( select id from t1 group by id having count(*) > 1 )
The query contains a correlated subquery in WHERE clause:
SELECT COUNT(*) FROM t1 WHERE t1.id = t.id
It is called correlated because it is related to the main query via t.id. So, this subquery counts the number of records having an id value that is equal to the current id value of the record returned by the main query.
Thus, predicate
(SELECT COUNT(*) FROM t1 WHERE t1.id = t.id) = 2
evaluates to true for any row with an id value that occurs twice in the table.
SELECT * FROM t1 AS t
WHERE 2 = (SELECT COUNT(*) FROM t1 WHERE t1.id = t.id);
This query goes through each record in t1 and then in the subquery looks into t1 again to see if in this case id is found 2 times (and only 2 times). You can do the same for any other column in t1 (or any table for that matter).
When you would like to see all values that are multiple times in the table, change WHERE 2 = by WHERE 1 <. This will also give you the values that are 3 times, 4 times, etc. in the table.
{
SELECT id,count( * )
FROM
MyTable
group by id
having count( * )>1
}
with this code, you can see the rows which repet more than one,
and you can change this query by yourself
How about using GROUP BY and HAVING:
SELECT id, count(1) as Total FROM MyTable AS t1
GROUP BY t1.id
HAVING Total = 2
I have a database with 2 tables. table1 and table2.
Table1 contains a list of tests ( column 'name' ). And I want to count how many rows are missing in table2 ( this table has also a column 'name' ) according to the list of tests of table1.
So I just want to count the mismatch between table1.name and table2.name.
I tried several querys, but all didnt really work.
I tried to use the 'NOT IN' statement but it takes too much time. Like several minutes.
For example, the output should be :
COUNT(*) = 20
It means that 20 tests are missing ( or not done yet ) in table2.
I'm using MySQL, so I can't use EXCEPT or MINUS statement.
Thank you by advance.
Nordine
You can use not exists :
select count(*)
from table1 t1
where not exists (select 1 from table2 t2 where t2.name = t1.name);
If you have a duplicate name in table1 then you need count(distinct t1.name) instead.
Try the below query:
select count(case when bname is null then 1 end)
from
(
select a.name as aname, b.name as bname from
table1 a left join table2 b
on a.name=b.name)x
MINUS can be used in MySQL.
Ref:http://www.mysqltutorial.org/mysql-minus/
Try this:
SELECT name
FROM table1
MINUS
SELECT name
FROM table2
I need to join two tables in SQL. There are no common fields. But the one table have a field with the value krin1001 and I need it to be joined with the row in the other table where the value is 1001.
The idea behind the joining is i have multiple customers, but in the one table there customer id is 'krin1001' 'krin1002' and so on, in this table is how much they have sold. In the other table there customer is is '1001' '1002' and so on, and in this table is there name and adress and so on. So it will always be the first 4 charakters i need to strip from the field before matching and joining. It might not always be 'krin' i need it to work with 'khjo1001' also, and it still needs to join on the '1001' value from the other table.
Is that possible?
Hope you can help me.
You need to use substring:
ON SUBSTRING(TableA.Field, 5, 4) = TableB.Field
Or Right:
ON RIGHT(TableA.Field, 4) = TableB.Field
You can also try to use CHARINDEX function for join operation. If value from table1 contains value from table2 row will be included in result set.
;WITH table1 AS(
SELECT 'krin1001' AS val
UNION ALL
SELECT 'xxx'
UNION ALL
SELECT 'xyz123'
),
table2 AS(
SELECT '1001' AS val
UNION ALL
SELECT '12345'
UNION ALL
SELECT '123'
)
SELECT * FROM table1 AS t
JOIN table2 AS T2 ON CHARINDEX(T2.val, T.val) > 0
Use it as:
SELECT
*
FROM table t1
INNER JOIN table t2 ON RIGHT(t1.col1, 4) = t2.col1;
the case is that I need to select a field distinct from table1 (no duplicates) and use the result as a key to select from another table2. And I need this to be in one query. Is this possible?!
table1: hID, hName, hLocation
table2: hID, hFrom, hTo, hRate, hRoomType, hMeals
I want to correct version of this query:
SELECT
*
FROM
table1
JOIN (
DISTINCT
hID
FROM
table2
WHERE
hRoomType = Double Room
ON table1.hID = table2.hID)
expected result: all hotels that offer Double Room thanks much –
thanks for help!
Your question is quite vague and confusing. Is this what you are looking for:
SELECT hID, name, location
FROM table2
INNER JOIN table1
ON table1.hID = table2.hID
GROUP BY table2.hID;
Here is a skeleton to achieve this:
SELECT
* -- Don't forget to list the requested fields instead of using `*`!
FROM (
-- This is the distinct list from table1
SELECT DISTINCT
id
FROM
table1 T1
) DT1
INNER JOIN table2 T2
ON T1.id = T2.reference_to_t1_id
Another solution if you don't want to retrieve any columns from table1:
SELECT
* -- Don't forget to list the requested fields instead of using `*`!
FROM
table2 T2
WHERE
-- Sais that get all record from table2 where this condition matches
-- at least one record
EXISTS (
SELECT 1 FROM table1 T1 WHERE T1.id = T2.reference_to_t1_id
)
For your tables and question
SELECT
hID, hName, hLocation
FROM
table1 T1
WHERE
EXISTS (
SELECT 1 FROM
table2 T2
WHERE
T1.hID = T2.hID
AND T.hRoomType = 'Double' -- Assuming that this is the definition of double rooms
)