I have one table of like this
user|itemID
and another table like this:
itemID | itemTrait1 | itemTrait2 etc...
I am trying to link the tables in one query which should be simple. I conduct the query like so:
SELECT * FROM Table1, Table2 WHERE Table1.userID = 1 AND Table1.itemID = Table2.itemID;
The issue is that I am getting 456 results returned but if I simply run:
SELECT * FROM Table1 WHERE userID = 1;
I get 434 results. Should both these statements get the same number of results returned?
How I imagine this call working is that for every entry in Table 1 for user 1 it connects it to the item's data in Table2? I think I am missing something here.
Query to combine both tables based in itemID
select * from table1 t1
left join table t2 on t1.itemID = t2.itemID
where t1.itemID = 1;
if you are getting the more records than the records that of table1 then your second table table2 must have multiple records for itemID. for example
Table1
user | itemId
---------------
1 | 1
Table2
itemId | itemTrait1 | itemTrait2
----------------------------------------
1 | A | B
1 | C | D
now when you will apply join here it will join itemID 1 with two items of second table.
Related
I am trying to work out how to perform an SQL UPDATE table column from Table A into Table B. The problem I have is trying to concat multiple values from Table A Column X into Table B Column Y
TableA Structure
id | Interest
1 | Bowling
2 | Swimming
1 | Basketball
TableB Structure
id | Interest_new
1 | null
2 | null
I want Table B to have following data
TableB
id | Interest_new
1 | Bowling,Basketball
2 | Swimming
This is my attempt with SQL query but it doesn't concat , just updated table B with first match
UPDATE TableB
INNER JOIN TableA ON TableB.id= TableA.id
SET TableB.id=CONCAT(TableA.id, ',')
where TableA.id= TableB.id;
You probably intend to use GROUP_CONCAT here, as you want an aggregated CSV output:
UPDATE TableB b
INNER JOIN
(
SELECT id, GROUP_CONCAT(Interest ORDER BY id) Interests
FROM TableA
GROUP BY id
) a
ON a.id = b.id
SET
Interest_new = a.Interests;
However, I actually advocate not even doing this, as storing CSV in your SQL tables is a generally bad idea. Consider just making a view of this data instead:
CREATE VIEW newInterests AS
SELECT id, GROUP_CONCAT(Interest ORDER BY id) Interests
FROM TableA
GROUP BY id;
example table:
id | value
----------
1 | abc
1 | cb3
1 | dsf
2 | sss
2 | d3
So if the input is "cb3" I want to get all rows with id 1, if the input is "sss" I want to get all rows with id 2. Can this be done with one query instead of two ? (first query is find id and second query bring rows for found id). Also, would a one query approach be faster ?
Thank you in advance.
you could try this :
SELECT *
FROM TABLE my_table
WHERE id IN (SELECT id
FROM TABLE my_table
WHERE value = input
)
Try the following, where you replace 'sss' with the value you are searching for:
select * from table t1
where t1.id in (select id from table t2 where value = 'sss')
Note that value seems not to be a key, such that you might get two different groups of ids in your result. That's also the reason why I proposed an t1.id IN (select id ... rather than an t1.id = (select id ....
You can solve it using inner join also.
SELECT S.*
FROM dataset AS S
INNER JOIN dataset AS T
ON S.id = T.id
WHERE T.value = 'cb3';
I have 2 tables. In first table
id book_name date
--------------------------
2 php 12-10-2015
3 java 12-10-2015
---------------------------
in the second table
id book_1 book_2
-------------------
12 2 3
------------------
now what will be the SQL query for viewing like this when search in SQL
id book_1 book_2
---------------------
12 php java
---------------------
You are looking for JOIN.
You JOIN table2 with table1 twice, using ALIAS to difference between them.
SELECT T2.id, A.book_name, B.book_name
FROM Table2 T2
JOIN Table1 A
ON T2.book_1 = A.id
JOIN Table1 B
ON T2.book_2 = B.id
I'm trying to sum certain rows from a hash table using two elements: a select group of IDs and a particular key.
Here's the setup:
Table 1:
ID KEY VALUE
1 name John Doe
1 amount 10
2 name Jane Doe
2 amount 15
3 name Mike Lowry
3 amount 5
Table 2:
ORDERID TYPE TRANSACTIONID
1001 Purchase 1
1002 Donation 2
1003 Purchase 3
I'm trying to get a sum of all the amounts where the type is "Purchase." Here's the query I'm using:
SELECT SUM(Table1.value) as balance
FROM Table1
LEFT JOIN (SELECT Table2.TRANSACTIONID as TID FROM Table2 WHERE Table2.TYPE = "Purchase" ) as ids
ON Table1.ID = ids.TID
WHERE Table1.key = "amount"
Tweaking that, I've managed to get 0 and the total of all the rows, but not just the one result. Ideas?
The problem is that your query makes an outer join between Table1 and Table2, such that all records of Table1 are preserved irrespective of whether a matching record is found from Table2. Learn about SQL joins.
You want to make an inner join instead:
SELECT SUM(VALUE)
FROM Table1 JOIN Table2 ON Table1.ID = Table2.TRANSACTIONID
WHERE Table1.KEY = 'amount' AND Table2.TYPE = 'Purchase'
See it on sqlfiddle.
I have two tables one with ID and NAME
table 1
ID | NAME
1 | first
2 | second
3 | third
and an XREF table with ID and PARENT ID
table2
ID | PARENT ID
1 | 0
2 | 1
3 | 2
and I would like to retrieve the NAME twice like this: NAME | PARENT NAME
If it is possible to go three levels deep but with same 2-column table like this:
result table
NAME | PARENT NAME
first | NULL or EMPTY or this line the not showing at all
second | first
third | second
... then I'd like to figure that out as well.
select t1.Name, t12.Name from
table1 t1
inner join table2 t2 on t1.ID = t2.ID
inner join table1 t12 on t2.ParentID = t12.ID
This would only return 2 rows. If you want to have the first row (for ID=1) you just need to outer join instead.
Consider putting the parentid in the first table as a self-referential relationship rather than having a separate table for it.
Ex.:
table1
ID | PARENTID | NAME
---------------------------
1 NULL first
2 1 second
3 2 third
That way you would only need to join the table on itself rather than going through a 3rd table. (This is however assuming that the rows in table1 can only have a single parent, whereas your design allows one row to have multiple parents at a time)
But for your table structure, this will work:
SELECT
a.name,
c.name AS 'PARENT NAME'
FROM
table1 a
LEFT JOIN
table2 b ON a.id = b.id
LEFT JOIN
table1 c ON b.parentid = c.id
But if you made the parentid in the same table referencing id, the SQL would be reduced to this:
SELECT
a.name,
b.name AS 'PARENT NAME'
FROM
table1 a
LEFT JOIN
table2 b ON a.parentid = b.id