Trying to explain my Question:
Say, Table A contains ID,Number,Location.
Table B contains Option 1,Option 2.
I want to write a single query that would select ID, Number & Option 1 from the Table A and Table B.
(At present I am doing something like:
SELECT ID FROM [A]
SELECT Option 1 FROM [B]
)
You do this:
SELECT A.ID, A.Number, B.Option1
FROM TableA as A, TableB as B
WHERE A.id = B.id;
This Part sets an alias for the table so that you don't have type in the full table name all the time:
TableA as A
TableB as B
This part is the relationship between table A and B.
WHERE A.id = B.id;
Consider reading SQL table relationships http://net.tutsplus.com/tutorials/databases/sql-for-beginners-part-3-database-relationships/
Related
I have table A and table B with different number of columns but both containing a column with IDs. Table A contains more complete list of IDs and table B contains some of the IDs from the table A.
I would like to return resulting table B with original information plus appended IDs that are missing in B but contained in A. For these appended rows, other columns should be blank while column with IDs in B should just contain missing ID values.
Simple solution UNION ALL, with NOT EXISTS:
select b.id, b.c1, ..., b.cn
from b
UNION ALL
select distinct a.id, null, ..., null -- should be same number of columns as in the above select
from a
where not exists (select 1 from b where b.id = a.id)
I think you described left join:
select *
from b left join
a
using (id)
I am trying to retrieve the IDs from a table in Oracle only IF another column value doesn't exist in any of the joined tables. Let me give you an example:
example
As you can see in the sketch, Table A is joined to tables B via the ID. I would like to get the IDs from Table A only if all statuses in any joined Table B DO NOT contain the value 2.
Here is my SQL statement:
SELECT ID FROM TABLE A
LEFT JOIN TABLE B
ON A.ID = B.REF_ID
WHERE B.STATUS NOT IN (2)
Unfortunately, I still get all IDs (which makes sense) and am not able to come up with a method to retrieve only the IDs without a certain value in the Status column of a joined table. Hence, I would only like to get ID 1, since all joined tables do not contain the value 2 in their Status.
Many thanks for any inputs.
Use aggregation
SELECT ID
FROM TABLE A LEFT JOIN
TABLE B
ON A.ID = B.REF_ID
GROUP BY A.ID
HAVING SUM(CASE WHEN B.STATUS IN (2) THEN 1 ELSE 0 END) = 0;
Or, simply use NOT EXISTS:
SELECT A.ID
FROM TABLE A
WHERE NOT EXISTS (SELECT 1
FROM B
WHERE A.ID = B.REF_ID AND B.STATUS IN (2)
);
I have 2 Tables, that related with third by one-to-many relation.
For example I have Table A, Table B and Table C.
Table A and B related with table C as many-to-one. So in Table C I have 2 fields like tableAId and tableBId. As a result I need to find a list which includes all Elements from table C which related with table A and compare them to all elements from table C which related with table B.
I tried do it with except, minus statements, but it works incorrect.
Here is what I try to do:
SELECT tableAId FROM tableC
except
select tableBId FROM tableC
UPDATE
Here is my 3 tables :enter image description here
I'm not 100% following what you require but i think below is what you want
SELECT a.ID, b.ID
FROM TableA a
JOIN TableC c ON a.ID = c.TableCID
JOIN TableB b ON c.TableBID = b.ID
I'm just curious, if i have table a and table b.
I write query 1:
SELECT * FROM table a INNER JOIN table b ON table a.id = table b.id
I write query 2:
SELECT * FROM table b INNER JOIN table a ON table b.id = table a. id
What is the difference both of above query?
Thank you
When using INNER JOIN , there is no difference in resultset returned except in order of columns when SELECT * is used i.e. columns are not explicitly mentioned.
SELECT *
FROM table a
INNER JOIN table b
ON table a.id = table b.id
returns columns from tableA followed by columns from tableB
SELECT *
FROM table b
INNER JOIN table a
ON table b.id = table a. id
returns columns from tableB followed by columns from tableA
The second table matches data with the first one.
So it is better to put smaller table on the second place.
Is it possible to include table name in the returned column if I use wildcard to select all columns from tables?
To explain it further. Suppose I want to join two tables and both tables have the column name “name” and many other columns. I want to use wildcard to select all columns and not explicitly specifying each column name in the select.
Select *
From
TableA a,
TableB b
Where
a.id = b.id
Instead of seeing two column with same name "name", could I write a sql to return one column name as "a.name" (or TableA.name) and one as "b.name"(or TableB.name) without explicitly putting the column name in select?
I would prefer a solution for mssql but other database could be a reference too.
Thanks!
You can use select a.*, ' ', b.* from T1 a, T2 b to make it more visible where columns from T1 end and columns from T2 begin.
You are basically joining two tables on the ID field, so you will only see one column labeled "ID", not two, because you are asking to see only those records where the ID is the same in table a and table b: they share the same id.
Try ...
SELECT 'TableA' AS 'Table', A.* FROM TableA A
WHERE A.id IN (SELECT id FROM TableB)
UNION
SELECT 'TableB' AS 'Table', B.* FROM TableB B
WHERE B.id IN (SELECT id FROM TableA)
ORDER BY id, [Table]