If I have Table1 as
A B C
1 b.1 c.1
2 b.2 c.2
1 b.3 c.3
My second table Table2 as
A D E F G
1 d.1 e.1 f.1 g.1
2 d.2 e.2 f.2 g.2
I need to insert into an empty Table3 the values from above such that it looks like this.
A B C D E
1 b.1 c.1 d.1 e.1
2 b.2 c.2 d.2 e.2
1 b.3 c.3 d.1 e.1
So basically I need to insert each row of Table1 into Table3. For each row I need to check for column A and find the corresponding value D and E from the column and insert into Table3. Is it possible to do this in one single query?
To copy Table1 to Table3 I can use the query
INSERT INTO Table3(A,B,C) SELECT A,B,C FROM Table1
And then I need to take each row from Table3 and using A update the values of D and E from Table2. Is there a better solution that I can use to insert directly from both tables to Table3? Any help is appreciated, as I am a beginner with database and queries.
To merge two tables, use a join:
-- INSERT ...
SELECT A, B, C, D, E
FROM Table1
JOIN Table2 USING (A);
This will not generate a result row if no matching Table2 row is found. If you want a result row in this case (with NULLs for the missing values), use an outer join instead.
INSERT INTO Table3 (A,B,C,D,E)
SELECT t1.A, t1.B, t1.C, t2.D, t2.E FROM Table1 t1
INNER JOIN Table2 t2 ON t2.A = t1.A
This might solve your problem.
Related
I’m new to SQL and I’m using MS Access 2016. I created a query using Table1 and Table2.
Table1 holds the data A, B, C, D.
Table2 holds values (the letters are T2Data1; and numbers are T2Data2): A 2, A 6, B 3, & D 4.
The query is:
SELECT Table1.T1Data1, Sum(Table2.T2Data2) AS SumOfT2Data2
FROM Table1 INNER JOIN Table2 ON Table1.T1Data1 = Table2.T2Data1
GROUP BY Table1.T1Data1;
Ideally I want the output to be:
A 8
B 3
C
D 4
I can get A, B, & D but I can't get the blank for C. How do I do that?? Any help is much appreciated!!
Use an outer join:
SELECT Table1.T1Data1, Sum(Table2.T2Data2) AS SumOfT2Data2
FROM Table1
LEFT JOIN Table2 ON Table1.T1Data1 = Table2.T2Data1
GROUP BY Table1.T1Data1
A Visual Explanation of SQL Joins
SQL Fiddle Demo
If you want to return 0 instead of null, you may need to use nz() which is similar to coalesce.
Given the following 2 rows of data:-
ColumnA ColumnB ColumnC ColumnD
33 10298 11588 4474.32
33 10298 11588 2237.16
How do I go about writing a T-SQL query which will remove only the first data row where ColumnsA - C are the same and the value in ColumnD is double that of the second data row.
It doesn't have to particularly performant as I am only removing approximately 500 rows.
Something along these lines should work:
DELETE FROM t2
FROM table t1
inner join
table t2
on
t1.ColumnA = t2.ColumnA and
t1.ColumnB = t2.ColumnB and
t1.ColumnC = t2.ColumnC and
t1.ColumnD * 2 = t2.ColumnD
This assumes that if you have 3 rows where their ratios between columnD values are 1 : 2 : 4, you want to delete both the 2 and 4 rows. If that's not the case, please consider such a situation and let me know what should happen there.
DELETE documentation
Complete script:
create table T (A int,B int, C int, D int)
insert into T(A,B,C,D)
values (1,2,3,4),(1,2,3,8)
delete from t2
from t t1
inner join
t t2
on
t1.A = t2.A and t1.B = t2.B and t1.C = t2.C and t1.D * 2 = t2.D
select * from T
Result:
A B C D
----------- ----------- ----------- -----------
1 2 3 4
Try this solution:
delete from YourTable
from YourTable t1
where exists (select 1 from YourTable t2 where t1.ColumnA=t2.ColumnA and t1.ColumnB=t2.ColumnB and t1.ColumnC=t2.ColumnC and t1.ColumnD=t2.ColumnD*2)
You can't use the same table two times in a join statement, if You want delete from that table. So use istead the join an exists statement or join a derived table.
I have two tables in my database like this:
Table-1 Table-2
id Name id Name
1 A 1 D-a
2 B 2 D-b
3 C 3 D-c
4 D
I want a query which gives me output such as
A B C D-a D-b D-c
i.e. check if there is entry of D in Table-1 if there is then select all entries of Table-2 and remove D from output
I think this is not the best answer to your question, but it can help you:
Select Distinct Table1.name
From Table1, Table2
WHERE Not Table2.name Like Table1.name+'%'
UNION All
Select Distinct Table2.name
From Table1, Table2
WHERE Table2.name Like Table1.name+'%'
Now you have your results in a column.
If you want to have them in a row follow this question:
Concatenate many rows into a single text string
I need some help to calculate the rank from two table.
Suppose i have two table - table1 and table2.
In table1, i have below info
Disease value
A 20
B 10
C 35
In table2, i have below info
Diseaselist Othervalue
A 20
B 10
D 35
E 20
I want to check here, if A from table1 is available in table 2 then it will get high rank othewise less rank. Here C in table1 has more value than A but it is not available in table2 so it will get less rank than A and B.
Kindly sugges how would i accomplish this.
Regards,
Ratan
You can join the two tables using LEFT JOIN. And to order the rows, use CASE statement.
SELECT a.Disease, a.Value
FROM Table1 a
LEFT JOIN Table2 b
ON a.Disease = b.DiseaseList
ORDER BY CASE WHEN b.DiseaseList IS NULL THEN 1 ELSE 0 END,
a.Value DESC
I'm having trouble figuring this out.
According to Jeff Atwood A Visual Explanation of SQL Joins Left outer join produces a complete set of records from Table A, with the matching records (where available) in Table B. If there is no match, the right side will contain null.
The left table (TableA) doesn't have duplicates. The right tableB has 1 or 2 entries for each client number. The PrimaryTP designates one as primary with 1 and the other has 0.
I shouldn't have to include the line And B.PrimaryTP = 1 because TableA doesn't have duplicates. Yet if I leave it out I get duplicate client numbers. Why?
Can you help me understand how this works. It's being very confusing to me. The logic of And B.PrimaryTP = 1 escapes me. Yet it seems to work. Still, I'm scared to trust it if I don't understand it. Can you help me understand it. Or do I have a logic error hidden in the query?
SELECT A.ClientNum --returns a list with no duplicate client numbers
FROM (...<TableA>
) as A
Left Outer Join
<TableB> as B
on A.ClientNum = B.ClientNum
--eliminate mismatch of (ClientNum <> FolderNum)
Where A.ClientNum Not In
(
Select ClientNum From <TableB>
Where ClientNum Is Not Null
And ClientNum <> IsNull(FolderNum, '')
)
--eliminate case where B.PrimaryTP <> 1
And B.PrimaryTP = 1
The difference between an INNER JOIN and a LEFT JOIN is just that the LEFT JOIN still returns the rows in Table A when there are no corresponding rows in Table B.
But it's still a JOIN, which means that if there is more than one corresponding row in Table B, it will join the row from Table A to each one of them.
So if you want to make sure that you get no more than one result for each row in Table A, you have to make sure that no more than one row from Table B is found - hence the And B.PrimaryTP = 1.
If you have one client number in A and two matches in Table B, then you will get duplicates.
Suppose you have the following data,
Table-A(client Num) Table-B(client Num)
1 2
2 2
The left Join Results
Table-A(client Num) Table-B(client Num)
1 (null)
2 2
2 2
This is the cause of duplicates. So you need to take distinct values form Table B or perform Distinct on the result set.
I shouldn't have to include the line And B.PrimaryTP = 1 because TableA doesn't have duplicates. Yet if I leave it out I get duplicate client numbers. Why?
Because both rows in the right table match a row in the left table. There is no way for SQL Server to output a triangular result; it must show the columns from both tables for every joined row. And this is true for INNER JOIN as well.
DECLARE #a TABLE(a INT);
DECLARE #b TABLE(b INT);
INSERT #a VALUES(1),(2);
INSERT #b VALUES(1),(1);
SELECT a.a, b.b FROM #a AS a
LEFT OUTER JOIN #b AS b ON a.a = b.b;
SELECT a.a, b.b FROM #a AS a
INNER JOIN #b AS b ON a.a = b.b;
Results:
a b
-- ----
1 1
1 1
2 NULL
a b
-- --
1 1
1 1
On the link that you gave the joins are explained very good. So the problem is that you have several records from table A (no matter that there are no duplicates) is that to 1 record in A there are 2 records in B (in some cases). To avoid this you can use either DISTINCT clause, either GROUP BY clause.
The LEFT OUTER JOIN will give you all the records from A with all the matching records from B. The difference with an INNER JOIN is that if there are no matching records in B, an INNER join will omit the record from A entirely, while the LEFT join will then still include a row with the results from A.
In your case, however, you may also want to check out the DISTINCT keyword.