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.
Related
I have this SQL problem: I have tables A and B. Table A has columns id and name, Table B amount and id which is a foreign key to table A.id.
I need to return all table A rows that don't have their id stored in table B. Any ideas?
So the complete opposite is:
SELECT *
FROM a
LEFT OUTER JOIN b ON a.id = b.id;
Here row what I need is left out of result
Just add a where clause:
SELECT a.*
FROM a LEFT OUTER JOIN
b
ON a.id = b.id
WHERE b.id IS NULL;
You can also use NOT EXISTS:
select a.*
from a
where not exists (select 1 from b where b.id = a.id);
In most databases, the two methods typically have similar performance.
I am wondering how to use oracle sql to get all the rows that are in one table but not another. The issue I am having is that the two tables don't have a field in common so I need to join to a third master table.
This is what I've tried which doesn't produce any errors but also produces 0 records which isn't possible but clearly I've done something wrong.
SELECT a.USER_ID, c.AD_ID, c.CREATED_DATE_ FROM $A$ a, $C$ c, $B$ b
WHERE (b.USER_ID IS NULL AND a.CUSTOMER_ID = c.CUSTOMER_ID)
I have three tables:
Table A has fields CUSTOMER_ID & USER_ID
Table B has field USER_ID
Table C has field CUSTOMER_ID
I need all the users that are in table C but not table B. They are all in Table A because that is the master list of users.
Any insight would be greatly appreciated.
SELECT
*
FROM
table_a
WHERE
NOT EXISTS (SELECT * FROM table_b WHERE table_b.user_id = table_a.user_id )
AND EXISTS (SELECT * FROM table_c WHERE table_c.customer_id = table_a.customer_id)
My solution:
select * from TableC tc
join TableA ta on tc.CUSTOMER_ID=ta.CUSTOMER_ID
left join TableB tb on tb.USER_ID=ta.USER_ID
where ta.USER_ID is null
I think you want:
select a.USER_ID, c.AD_ID, c.CREATED_DATE_
from a join
c
on a.customer_id = c.customer_id
where not exists (select 1 from b where b.user_id = a.user_id);
SQL:
WITH joined AS (
SELECT *
FROM table_a a
JOIN table_b b ON (a.a_id = b.a_id)
)
SELECT a_id
FROM joined
returns invalid identifier.
How can you select joined column when using WITH clause? I have tried aliases, prefixing and nothing worked. I know I can use:
WITH joined AS (
SELECT a.a_id
FROM table_a a
JOIN table_b b ON (a.a_id = b.a_id)
)
SELECT a_id
FROM joined
but I need this alias to cover all fields.
Only way I managed to meet this condition is using:
WITH joined AS (
SELECT a.a_id a_id_alias, a.*, b.*
FROM table_a a
JOIN table_b b ON (a.a_id = b.a_id)
)
SELECT a_id_alias
FROM joined
but it is not perfect solution...
You can use the effect of the USING clause when joining the tables.
When you join tables where the join columns have the same name (as it is the case with your example), the USING clause will return the join column only once, so the following works:
with joined as (
select *
from table_a a
join table_b b using (a_id)
)
select a_id
from joined;
SQLFiddle example: http://sqlfiddle.com/#!4/e7e099/2
I don't think you can do this without aliases. The result of the "joined" query has two fields, both named a_id. Unless you alias one (or both), as you did in your final query, the outer query has no idea which a_id you are referring to.
Why is your final query not a "perfect" solution?
You can probably use alias as below:
WITH JOINED AS (
SELECT A.A_ID A_A_ID, B.A_ID B_A_ID,
A.FIELD_NAME1 A_FIELDNAME1, A.FIELDNAME2 A_FIELDNAME2,A.FIELDNAME_N A_FIELDNAME_N,
B.FIELD_NAME1 B_FIELDNAME1, B.FIELDNAME2 B_FIELDNAME2,B.FIELDNAME_N B_FIELDNAME_N,
FROM TABLE_A A
JOIN TABLE_B B ON (A.A_ID = B.A_ID)
)
SELECT A_A_ID, B_A_ID
FROM JOINED
IT IS ALWAYS A GOOD PRACTICE TO AVOID USING SELECT *
I am a beginner with SQL and I have a question regarding finding a subset of data that does not exist in another table.
Currently I have 2 tables
Table A has a single column of OrderID containing about 300 records
Table B also has a single column containing 1000 records
How do I write a SQL query that helps me identify the 700 records not in Table A?
Thank you
You need to use NOT IN.Try this:
SELECT * FROM TableB
WHERE OrderID NOT IN (SELECT OrderID FROM TableA)
OR
Use a join.
SELECT B.*
FROM TableB B LEFT JOIN TableA A ON A.OrderID = B.OrderID
WHERE A.OrderID IS NULL
Try this:
SELECT TableB.* FROM TableB LEFT JOIN TableA ON TableĐ’.OrderID = TableA.OrderID WHERE TableA.OrderID is NULL;
I have the following problem:
In DB, I have two tables. The value from one column in the first table can appear in two different columns in the second one.
So, the configuration is as follows:
TABLE_A: Column Print_group
TABLE _B: Columns Print_digital and Print_offset
The value from the different rows and Print_group column of the Table_A can appear in one row of the Table_B but in different column.
I have the following query:
SELECT DISTINCT * FROM Table_A
INNER JOIN B ON (Table_A. Print_digital = Table_B.Print_group OR
Table_A.Print_offset = Table_B.Print_group)
The problem is that this query returns the same row from the Table_A two times.
What I am doing wrong? What is the right query?
Thank you for your help
If I'm understanding your question correctly, you just need to clarify your fields to come from Table_A:
SELECT DISTINCT A.*
FROM Table_A A
INNER JOIN B ON A.Print_digital = B.Print_group
OR A.Print_offset = B.Print_group
EDIT:
Given your comments, looks like you just need SELECT DISTINCT B.*
SELECT DISTINCT B.*
FROM Table_A A
INNER JOIN B ON A.Print_digital = B.Print_group
OR A.Print_offset = B.Print_group
I've still another question... first,to be clear, the right query version is
SELECT DISTINCT A.*
FROM Table_A A
INNER JOIN B ON A.Print_digital = B.Print_group
OR A.Print_offset = B.Print_group.
If I want it returns also one column from the B table it again returns duplicate rows. My query (the bad one) is the following one:
SELECT DISTINCT A.*, B.Id
FROM Table_A A
INNER JOIN B ON A.Print_digital = B.Print_group
OR A.Print_offset = B.Print_group