I have 2 database tables. Table A has to fetch some records based on parameter passed there may or may not be an entry in table B with that key.
What I want to do is:
select a.col1,a.col2,a.col3
FROM table WHERE a.id = 123
This would fetch 20 rows. For one of the rows there is an entry in another table B.
select T_level from table b where b.id = 123
only one record appears with right value.
What I want is to get this in a single query. Something like:
select a.col1,a.col2,a.col3,b.T_level
from a,b
where a.id = 123
and a.id = b.id
When I do that, I get 20 rows and the column T_level as '50' for all the rows, whereas it should be '50' for one correct row, for rest it should be null.
I further tried:
select a.col1,a.col2,a.col3,nvl(b.T_level,0) from a,b
but that doesn't fetch the way I expect.
Firstly, please learn to use ansi sql join syntax. The Oracle join syntax you are using hasn't been considered good practice for decades
SQL Join syntax
If you want to get all records from a and any matching records from b then you need to use a LEFT OUTER JOIN
Related
Questions similar to this one about using DISTINCT values in an INNER JOIN have been asked a few times, but I don't see my (simple) use case.
Problem Description:
I have two tables Table A and Table B. They can be joined via a variable ID. Each ID may appear on multiple rows in both Table A and Table B.
I would like to INNER JOIN Table A and Table B on the distinct values of ID which appear in Table B and select all rows of Table A with a Table A.ID which appears matching some condition in Table B.
What I want:
I want to make sure I get only one copy of each row of Table A with a Table A.ID matching a Table B.ID which satisfies [some condition].
What I would like to do:
SELECT * FROM TABLE A
INNER JOIN (
SELECT DISTINCT ID FROM TABLE B WHERE [some condition]
) ON TABLE A.ID=TABLE B.ID
Additionally:
As a further (really dumb) constraint, I can't say anything about the SQL standard in use, since I'm executing the SQL query through Stata's odbc load command on a database I have no information about beyond the variable names and the fact that "it does accept SQL queries," ( <- this is the extent of the information I have).
If you want all rows in a that match an id in b, then use exists:
select a.*
from a
where exists (select 1 from b where b.id = a.id);
Trying to use join just complicates matters, because it both filters and generates duplicates.
I'm having a bit of a problem with a SQL Query that returns too many results. I'm fairly new to SQL so please bear with me.
Please see the following:
Table Structures
The Query that I use looks like:
SELECT TABLE_B.*
FROM
TABLE_A
JOIN
TABLE_B
ON
TABLE_A.COMMON_ID=TABLE_B.COMMON_ID
AND TABLE_A.SEQ_3C=TABLE_B.SEQ_3C
JOIN
TABLE_C
ON
TABLE_A.COMMON_ID=TABLE_C.EMPLID
WHERE
TABLE_B.ITEM_STATUS<>'C'
and TABLE_A.CHECKLIST_STATUS='I'
and TABLE_A.ADMIN_FUNCTION='ADMA'
and TABLE_A.CHECKLIST_CD='APPL'
and TABLE_A.COMMON_ID = '123456789'
and TABLE_C.ADMIT_TERM='2171'
and TABLE_C.INSTITUTION='SOMEWHERE'
I just want the results from Table_B and not what it's giving me.
Please explain this to me as I have spent 3 days on it non-stop.
What am I missing?
You want data from TABLE_B? Then select from it only and have the conditions on the other tables in your where clause.
The inner joins on the other tables serve as existence tests, I assume? Don't do that. You'd only multiply your records, just as you are doing now, only to have to dismiss duplicates later. That can cause bad performance on large tables and errors in more complicated queries. Use EXISTS or IN instead.
select *
from table_b
where item_status <> 'C'
and (common_id, seq_3c) in
(
select common_id, seq_3c
from table_a
where checklist_status = 'I'
and admin_function = 'ADMA'
and checklist_cd = 'APPL'
)
and common_id in
(
select EMPLID
from table_c
where admit_term = '2171'
and institution = 'SOMEWHERE'
);
SELECT DISTINCT TABLE_B.*
FROM
TABLE_A
JOIN
TABLE_B
ON
TABLE_A.COMMON_ID=TABLE_B.COMMON_ID
AND TABLE_A.SEQ_3C=TABLE_B.SEQ_3C
JOIN
TABLE_C
ON
TABLE_A.COMMON_ID=TABLE_C.EMPLID
WHERE
TABLE_B.ITEM_STATUS<>'C'
and TABLE_A.CHECKLIST_STATUS='I'
and TABLE_A.ADMIN_FUNCTION='ADMA'
and TABLE_A.CHECKLIST_CD='APPL'
and TABLE_A.COMMON_ID = '123456789'
and TABLE_C.ADMIT_TERM='2171'
and TABLE_C.INSTITUTION='SOMEWHERE'
This should be easy to understand without looking at all your tables and output.
Suppose you join two tables, A and B, on a column id. You only want the columns from table B, and in table B the `id' column is a unique identifier.
Even so, if in table A an id (the same id) appears five times, the join will have five rows for that id. Then you just select the columns from table B, so it will look like you got the same row five different times.
Perhaps you don't really need a join? What is your underlying problem you are trying to solve?
It's hard to answer this question without more information about why you're executing these joins. I can explain why you're getting the results you're getting, and hopefully that will allow you to solve the problem yourself.
You start, in your FROM clause, with table A. You join this table with table B on matching COMMON_ID, which, based on the tables you provide, returns three matches for the one record you have in table A. This increases your result set size to three records. Next, you join these three records with table C, on matching ID. Because all ID's are, in fact, identical, this returns nine matches for every record in your current result set: you now have 9 x 3 = 27 records in your result set.
Finally, the WHERE clause comes into effect. This clause excludes 6 out of 9 records in table C, so you have 3 of those records left. Your final result set is therefore 1 (table A) x 3 (table B) x 3 (table C) = 9 records.
My code is such:
SELECT COUNT(*)
FROM earned_dollars a
LEFT JOIN product_reference b ON a.product_code = b.product_code
WHERE a.activity_year = '2015'
I'm trying to match two tables based on their product codes. I would expect the same number of results back from this as total records in table a (with a year of 2015). But for some reason I'm getting close to 3 million.
Table a has about 40,000,000 records and table b has 2000. When I run this statement without the join I get 2,500,000 results, so I would expect this even with the left join, but somehow I'm getting 300,000,000. Any ideas? I even refered to the diagram in this post.
it means either your left join is using only part of foreign key, which causes row multiplication, or there are simply duplicate rows in the joined table.
use COUNT(DISTINCT a.product_code)
What is the question are are trying to answer with the tsql?
instead of select count(*) try select a.product_code, b.product_code. That will show you which records match and which don't.
Should also add a where b.product_code is not null. That should exclude the records that don't match.
b is the parent table and a is the child table? try a right join instead.
Or use the table's unique identifier, i.e.
SELECT COUNT(a.earned_dollars_id)
Not sure what your datamodel looks like and how it is structured, but i'm guessing you only care about earned_dollars?
SELECT COUNT(*)
FROM earned_dollars a
WHERE a.activity_year = '2015'
and exists (select 1 from product_reference b ON a.product_code = b.product_code)
I'm using SQL Server 2005, and I have a script like this:
select INV_Nr, INV_Date, INV_Customer
from INVOICE A,
left outer join CANCEL_INVOICE B on B.INV_Nr = A.INV_Nr
So how can I add in 'where' clause / filter that all the INVOICE.INV_Nr that existed in CANCEL_INVOICE.INV_Nr will not show in the query result?
Thanks,
One way(probably the best), NOT EXISTS:
SELECT inv_nr,
inv_date,
inv_customer
FROM invoice i
WHERE NOT EXISTS(SELECT 1
FROM cancel_invoice c
WHERE c.inv_nr = i.inv_nr)
The LEFT OUTER JOIN approach might work but is less efficient and leads to incorrect (or at least unexpected) results, since there is no way to differentiate between a row that doesn't exist and a row that does exist but where that column is NULL.
Try this!!
It show all those invoice A.INV_Nr which is not exist in table CANCEL_INVOICE
SELECT INV_Nr, INV_Date, INV_Customer
FROM INVOICE A,
LEFT OUTER JOIN CANCEL_INVOICE B ON A.INV_Nr=B.INV_Nr
WHERE B.INV_Nr IS NULL
I have two tables with the same strucure. a.ID*(varchar(10)), a.CODE_ASS(varchar(1))* and b.ID*(varchar(10)), b.CODE_ASS(varchar(1))*
Table "a" contains 2010 data, and table "b" contain 2013 data.
These two tables should doesn't have the same number of rows in each, but common IDs should be identical. I need to compare tables and find differences.
As you can see in this example, green rows are ok, and red one should be an error.
ID 2, 4 and 5 are errors because there are some differences. ID 6, in "a" table, is ok even if it has been deleted in table "b".
It appears that you are using SQL tables, if you write a query to join the data on ID and select only where the values are different. Do you really want to assume that 0 = NULL?
SELECT a.ID FROM a INNER JOIN b ON a.ID = b.ID WHERE a.ID<>b.ID;
If you want 0 = NULL then you need to change NULLs to 0 - that would look like the following.
SELECT a.ID FROM a INNER JOIN b ON a.ID = b.ID WHERE ISNULL(a.ID,0)<>ISNULL(b.ID,0);
ISNULL(param, value) will change the NULL to the value, in this case 0.
I am guessing you are using a recordset object so then all you have to do is loop through the results.