English 中文(简体)
How to make a one to one left outer join?
原标题:
  • 时间:2009-11-09 20:07:11
  •  标签:
  • sql
  • oracle

I was wondering, is there a way to make a kind of one to one left outer join:

I need a join that matches say table A with table B, for each record on table A it must search for its pair on table B, but there exists only 1 record that matches that condition, so when it has found its pair on B, it must stop and continue with the next row at table A.

What I have is a simple LEFT OUTER JOIN.

select * from A left outer join B on A.ID = B.ID order by (NAME) asc

Thanks in advance!

最佳回答

The syntax you present in your question is correct. There is no difference in the query for joining on a one-to-one relationship than on a one-to-many.

问题回答

SQL doesn t work this way. In the first place it does not look at things row-by-row. In the second place what defines the record you want to match on?

Assuming you don t really care which row is selcted, something like this might work:

SELECT * 
From tableA
left outer join 
(select b.* from tableb b1
join (Select min(Id) from tableb group by id) b2 on b1.id - b2.id) b
on a.id = b.id

BUt it still is pretty iffy that you wil get the records you want when there are multiple records with the id in table b.





相关问题
Export tables from SQL Server to be imported to Oracle 10g

I m trying to export some tables from SQL Server 2005 and then create those tables and populate them in Oracle. I have about 10 tables, varying from 4 columns up to 25. I m not using any constraints/...

Connecting to Oracle 10g with ODBC from Excel VBA

The following code works. the connection opens fine but recordset.recordCount always returns -1 when there is data in the table. ANd If I try to call any methods/properties on recordset it crashes ...

How to make a one to one left outer join?

I was wondering, is there a way to make a kind of one to one left outer join: I need a join that matches say table A with table B, for each record on table A it must search for its pair on table B, ...

Insert if not exists Oracle

I need to be able to run an Oracle query which goes to insert a number of rows, but it also checks to see if a primary key exists and if it does, then it skips that insert. Something like: INSERT ALL ...

How can I store NULLs in NOT NULL field?

I just came across NULL values in NOT-NULL fields in our test database. How could they get there? I know that NOT-NULL constraints can be altered with NOVALIDATE clause, but that would change table s ...

Type reference scope

I m studying databases and am currently working on a object-relational DB project and I ve encountered a small problem with the number of possible constraints in an object table. I m using "Database ...

OracleParameter and DBNull.Value

we have a table in an Oracle Database which contains a column with the type Char(3 Byte). Now we use a parameterized sql to select some rows with a DBNull.Value and it doesn t work: OracleCommand ...

热门标签