I have two tables. The first table contains the code number, the second table contains the name corresponding to that code number. The first table has a source code number and a target code number. The second table contains both these code numbers in separate rows. So the tables look like this
Table1
|Source_code|Target_code|
|253 |568 |
Table2
|Code|Name |
|253 |John |
|568 |Steve|
I want a result like this:
|source_code|name |target_code|name |
|253 |John |568 |Steve|
I did this by joining both the tables twice in a single query, as follows:
select A.source_code, B.name, A.target_code, C.name
from table1 A
join table2 B on A.source_code = B.code
join table2 C on A.target_code = C.code
This doesn't look like the best way to handle this query. Is there a better way to do this?
Joining to table 2 twice is the way to handle this. Why? because you have in table1 TWO foreign keys to Table2. Since tables should be joined on keys and you have two keys to one table, your solution is almost appropriate.
The only issue I see is you should be joining on table2's code not the names.
SELECT A.source_code, B.name, A.target_code, C.name
FROM table1 A
INNER JOIN table2 B
on A.source_code = B.Code
INNER JOIN table2 C
on A.target_code = C.code
Related
I have two tables where main table has 10+ columns and second table has 3 columns with one common field. My problem here is I am not able to get exact count with left outer join as main table. I am seeing more count than actual. It might be due to one of the field I am trying to get is not in main table which is in second table.
Table 1: master_table
Table 2: manager_table
Master_table :
ID,
Column1,
Column2,
...
Column10
manager_table:
ID,
Column2_different,
Column3_different
I am trying to join using Left Join to get same records as present in master table.
Select table1.columns, table2.columns
From table1
Left join table2 on table1.ID = table2.ID
The above is not giving me exact record count as in master table (table1) , it is giving me more count as the table 2 other field is not present in table 1 .
Can someone help me here ?
TIA
I believe that an INNER JOIN would be better than a LEFT JOIN. Need some sample data to be sure, but if you're getting a higher count than you'd expect upon joining the tables this is probably because the LEFT JOIN is returning everything from both tables. An INNER JOIN will only return data that appears in both tables.
I face issue about duplicate data when join table, here my sample data table I have
-- Table A
I want to join with
-- Table B
this my query notation for join both table,
select a.trans_id, name
from tableA a
inner join tableB b
on a.ID_Trans = b.trans_id
and this the result, why I get the duplicating data which should show only two lines of data, please help me to solve this case.
Firstly, as you have been told multiple times in the comments, this is working exactly as you have written, and (more importantly) as intended. You have 2 rows in tableA and those 2 rows match 2 rows in your table tableB according to the ON clause. This means that each join operation, for the each of the rows in tableA, results in 2 rows as well; thus 4 rows (2 * 2 = 4).
Considering that your table, TableA only has one column then it seems that you should be cleaning up that data and deleting the duplicates. There are plenty of examples on how to do that already (example).
Perhaps the column you show us in TableA is one many, and thus instead you have a denormalisation issue, and instead there should be another table with the details of Id_trans and a PRIMARY KEY or UNIQUE CONSTRAINT/INDEX on it. Then you would join fron that table to TableB.
Finally, what you might be after is an EXISTS, which would look like this:
SELECT B.trans_id, B.[name]
FROM dbo.TableB B
WHERE EXISTS(SELECT 1
FROM dbo.TableA A
WHERE A.ID_Trans = B.trans_id); --Odd that it's called ID_Trans in one table, and Trans_ID in another
As the comments mentioned your query does exactly what you asked it to do but I think you wanted something like:
select a.trans_id, a.name, b.name
from tableA a
inner join tableB b on a.trans_id = b.trans_id
group by a.trans_id, a.name, b.name
Since there are two rows in both table with same ID join will make them four. You can use distinct to remove duplicates:
select distinct a.trans_id, name
from tableA a
inner join tableB b
on a.id_trans = b.trans_id
But I would suggest to use exists:
select trans_id, name
from tableB b
exists (select 1 from tableA a where a.trans_id=b.trans_id)
I have 2 tables in this format:
TABLE1: id | name | info
and
TABLE2: name | moreinfo
I have a query which returns a list of name's from the first table. I then want to use those to get the respective moreinfo from the other table. For example, if the names a, b were returned and and in TABLE 2 I had a | apple, b | bread I would want apple and bread returned.
Any thoughts on the best way to go about doing this? Any help appreciated, thank you!
It seems that you just want a join here:
SELECT t1.name, t2.moreinfo
FROM TABLE1 t1
INNER JOIN TABLE2 t2
ON t1.name = t2.name;
If you wanted to report all names in the first table, even if they had no matching names in the second table, you could use a left join instead:
SELECT t1.name, COALESCE(t2.moreinfo, 'NA') AS moreinfo
FROM TABLE1 t1
LEFT JOIN TABLE2 t2
ON t1.name = t2.name;
Literally you seem to ask for the Apple and Bread to be returned but not neccessarily other information associated with the name. It is unclear how the query results you have are formatted.
select moreinfo from table2 where name in (YOURQUERYRESULT);
YOURQUERYRESULT can be a query returning only the name or a list with the names.
The question is answered elsewhere with join examples where you might want to substitute table with the query you have.
select a.id, a.name, a.info, b.moreinfo
from (YOURQUERY) a
join table2 b on a.name=b.name
I suggest you add an id column in table2 to identify the user and join on that field. Names change and multiple users have the same name.
Best regards,
Bjarni
I have two tables, TableA:
- Original_Location
- Units
and TableB:
- Original_Loc
- Adjacent_Loc
- Direction (up/down/left/right from original loc)
My goal is to return the original location, the adjacent location, the direction, and the number of units at the adjacent loc. So far, I've only been able to return the units from the original loc.
Here is what I've tried so far:
Select Original_Location,
Units,
TableB.Adjacent_Loc,
TableB.Direction
From TableA
Inner Join
Select *
From TableB
On TableA.Original_Location = TableB.Original_Loc
My thought is that I might need to change the fields I'm selecting before the inner join, or potentially join on Original_Location = Adjacent_Loc.
Your Join syntax is not right. First you don't need to "select" anything from Table B, your initial SELECT is getting data from the joined tables (A and B) as if they were 1 table. Secondly, you need to specify which fields to join the tables with.
Your join will be something like :-
From TableA Inner Join TableB
on TableA.Original_Loc = TableB.Original_Loc
Once you have got your joins right, you need to make another join to TableA to get the Units. This time you are joining the Adjacent_Loc in Table B to the Original_Location in Table A - which will have the Units value you need.
My example below uses aliases to identify each table (there are now 2 references to TableA so they need to be identified separately). So when you do the second join to TableA, this has the alias of c to differentiate it from the first TableA reference. You then need to select the Units from c.
Select a.Original_Location, c.Units, b.Adjacent_Loc, b.Direction
From TableA a Inner Join TableB b On a.Original_Location = b.Original_Loc
inner join TableA c on b.Adjacent_Loc = c.Original_Location
I have several tables that I am joining that I need to add another table to and I can't seem to get the right query. Here is what I have now -
Table 1
carid, catid, makeid, modelid, caryear
Table 2
makeid, makename
Table 3
modelid, modelname
Table 4
catid, catname
The query I am using to join these is:
SELECT * FROM table1 a
JOIN table2 b on a.makeid=b.makeid
JOIN table3 c on a.modelid=c.modelid
JOIN table4 d on a.catid=d.catid
WHERE a.carid = $carid;
Now I need to add a 5th table that I am getting from a 3rd party that I am having a hard time adding to my existing query. The new table has these fields -
Table 5
id, year, make, model, citympg, hwympg
I need the citympg and hwympg based on caryear from table 1, makename from table 2, and modelname from table 3. I know I can do a second query with those values, but I would prefer to do a single query and have all of the data in a single row. Can this be done in a single query? If so, how?
it's possible to have more than condition in a join.
does this work?
SELECT a.*, e.citympg, e.hwympg
FROM table1 a
JOIN table2 b on a.makeid=b.makeid
JOIN table3 c on a.modelid=c.modelid
JOIN table4 d on a.catid=d.catid
Join table5 e on b.makename = e.make
and c.modelname = e.model
and a.caryear = e.year
WHERE a.carid = $carid;
...though your question is not clear. Did you only want to join table5 to the others, or was there something else you wanted to do with table5?
Without indexes, It won't be efficient, but you can do
LEFT JOIN table5 ON (table2.make = table5.make AND table3.model = table5.model AND table1.caryear = table5.caryear)
This also assumes the make and models and years strings match exactly.