I need to show only results which are in Table1 and Table2 but are not in Table3. Basically, it should be something like TABLE1, Table2 except INNER JOIN between (TABLE1, Table2) and TABLE3.
Should looks like this - On left side Table1 and Table2, on right side Table3
Now I have this:
SELECT mesta_email, mesta_kod
FROM Table1
UNION ALL
SELECT mesta_email, mesta_kod
FROM Table2
// And somehow except values which are in Table3
Can somebody help me please? Thanks a lot.
There are a couple different ways to do this. I believe mysql does better with the outer join/null approach:
select t.*
from (
SELECT mesta_email, mesta_kod
FROM Table1
UNION ALL
SELECT mesta_email, mesta_kod
FROM Table2
) t left join Table3 t3 on t.mesta_email = t3.mesta_email
and t.mesta_kod = t3.mesta_kod
where t3.mesta_email is null
This assume table3 shares the same structure as the other 2 tables.
I would approach the problem almost directly as you write it, using exists and not exists:
select t1.mesta_email, t2.mesta_kod
from table1 t1
where exists (select 1
from table2 t2
where t2.mesta_email = t1.mesta_email and t2.mesta_kod = t1.mesta_kod
) and
not exists (select 1
from table3 t3
where t3.mesta_email = t1.mesta_email and t3.mesta_kod = t1.mesta_kod
);
One advantage of exists/not exists over other approaches involves duplicates. If one of the tables (say table1) has not duplicates, but the others might, there is no need to remove duplicates in the resulting data set.
Related
For question purposes I will use minimal data for my examples.
I have a table called table1 and a column named test that looks like this:
test
5012
I am able to add an extra zero behind before the result of column test using this query:
SELECT CONCAT('0',test) as x from table1
this is the result of the query:
results table: table1
x
05012
Now I have another table called table2 looking like this:
test test2
05012 1
My question is, how do I join the two tables together based on that query above and concat the table1 with column test2 from table2? Making sure the first 4 characters of both columns test from both tables match together?
This is how table 1 should look like:
Afterquery
050121
I am curious why you wouldn't simply use table2?
select concat(t2.test, t2.test2) as afterquery
from table2 t2;
table1 doesn't seem to play a role.
If you want values in table2 filtered by table1, you can use exists:
select concat(t2.test, t2.test2) as afterquery
from table2 t2
where exists (select 1
from table1 t1
where t2.test = concat('0', t1.test)
);
You can express this as a join:
select concat(t2.test, t2.test2) as afterquery
from table2 t2 join
table1 t1
on t2.test = concat('0', t1.test);
This is useful if you want columns from both tables -- but that is not necessary to answer the question. On the other hand, this runs the risk of duplication if there are multiple matches.
I think that this should be the solution. You need to use concat in the join between table1 and table2
SELECT CONCAT('0', table1.test, table2.test2) AS Afterquery
FROM table1
INNER JOIN table2
ON CONCAT('0',table1.test) = table2.test
Slightly different approach with a sub-query:
select concat(concat_test, test2) test_results
from
(select concat('0', test) concat_test from table1) table_alias
join
table2 on substring(concat_test,1,4) = substring(test,1,4);
I've two tables, table1 contains 22780 rows. Now I left join table1 with table2 (which doesn't contain any duplicates) and I get 23588 rows.
SELECT * FROM Table1
left join Tabelle6 ON CAST(Table1.Customer AS Int) = table2.Customer
Why do I get more rows now? I only need every row from table1 once.
Edit: found my issue, table 2 does contain duplicates. But is there any way to join every row only once and ignore any further matches?
As the comment suggests, the easiest way to handle this would probably be to do SELECT DISTINCT to remove duplicates from your result set:
SELECT DISTINCT
t1.col1,
t1.col2,
t1.Customer,
...
FROM Table1 t1
LEFT JOIN Table2 t2
ON CAST(t1.Customer AS Int) = t2.Customer
But there is another option here. We could also join to a subquery which removes duplicate customers. This would ensure that no record from the first table gets duplicated from matching to more than one record in the second table.
SELECT *
FROM Table1 t1
LEFT JOIN
(
SELECT DISTINCT Customer
FROM Table2
) t2
ON CAST(t1.Customer AS Int) = t2.Customer
I have 2 tables t1 and t2. Each have a customer ID column. What I am looking for is to join the 2 columns and SUBTRACT the duplicates.
My EG:
Table1 and Table2 with the IDs for each
I have tried a union query. The result I am left with is ID = 1,2,3,4,5,6,7,8,9,10. Where, what I'm after is subtracting 1-5 from Table2 and the result = 6,7,8,9,10.
I hope that makes sense and that someone is able to help. Sorry if this is a bit too simple compared to what you're all used to.
In SQL Server you can use the EXCEPT operator:
select ID
from Table2
except
select ID
from Table1
Mysql does not support it though. Using a an in clause or a left join would work in both servers:
--Using In clause
SELECT ID
FROM Table2
WHERE ID NOT IN
(
SELECT ID
FROM Table1
);
--Using join
SELECT Table2.ID
FROM Table2
left join Table1
on Table2.ID = Table1.ID
where Table1.ID is null
Use left outer join
select * from t1 left outer join t2 on t1.customerid = t2.customerid
I have 2 tables:
table1 (id,usedcode)
table2 (codeid,uniquecode)
I want to be able to check if a certain value exists in uniquecode of Table2, but is not already used in Table1
Try using left join as below:
SELECT t2.*
FROM table2 t2 LEFT JOIN table1 t1
ON t2.uniquecode = t1.usedcode
WHERE t1.usedcode IS null
SELECT uniquecode FROM Table2
WHERE NOT EXISTS(
SELECT * FROM Table1 WHERE usedcode = uniquecode
)
In English the query is saying, "Select all unique codes from table 2 that don't exist in table 1 as a usedcode".
I'm desperate with this query. I have two tables table1 and table2, tables are identical but they have different data. I'm trying to remove duplicities by columns code and manufacturer. To do that I need in final result ID from table1 ID from table2 and also columns code and manufacturer
SELECT * FROM (
SELECT id,code,manufacturer FROM table1 WHERE manufacturer = 1
UNION SELECT id,code,manufacturer FROM table2 WHERE manufacturer = 1
) AS t GROUP BY code HAVING COUNT(*) > 1
But in result i got only values from table1. It's OK but I just need to get there id from table2 too. Please can anyone give me some tips how to do this ?
You have two basic problems:
Problem 1:
You are using UNION when you should be using UNION ALL, because UNION removes duplicates!
Problem 2:
This isn't the right way to go about the problem. You should be using a simple join, not a union.
Try this:
SELECT
t1.id as table1_id,
t2.id as table2_id,
t1.code,
t1.manufacturer
FROM table1 t1
JOIN table2 t2
ON t2.code = t1.code
AND t2.manufacturer = t1.manufacturer
WHERE manufacturer = 1 -- this WHERE clause is optional
Your use of the WHERE clause is a little odd - consider removing it to get all duplicates from all manufacturers.