I need to do a query to return the next (or prev) record if a certain record is not present. For instance consider the following table:
ID (开发者_JAVA技巧primary key) value
1 John
3 Bob
9 Mike
10 Tom.
I'd like to query a record that has id 7 or greater if 7 is not present.
My questions are,
- Are these type of queries possible with SQL?
- What are such queries called in the DB world?
Thanks!
Yes, it's possible, but implementation will depend on your RDBMS.
Here's what it looks like in MySQL, PostgreSQL and SQLite:
select ID, value
from YourTable
where id >= 7
order by id
limit 1
In MS SQL-Server, Sybase and MS-Access:
select top 1 ID, value
from YourTable
where id >= 7
order by id
In Oracle:
select * from (
select ID, value
from YourTable
where id >= 7
order by id
)
where rownum = 1
In Firebird and Informix:
select first 1 ID, value
from YourTable
where id >= 7
order by id
In DB/2 (this syntax is in SQL-2008 standard):
select id, value
from YourTable
where id >= 7
order by id
fetch first 1 rows only
In those RDBMS that have "window" functions (in SQL-2003 standard):
select ID, Value
from (
select
ROW_NUMBER() OVER (ORDER BY id) as rownumber,
Id, Value
from YourTable
where id >= 7
) as tmp --- remove the "as" for Oracle
where rownumber = 1
And if you are not sure which RDBMS you have:
select ID, value
from YourTable
where id =
( select min(id)
from YourTable
where id >= 7
)
Try this for MS-SQL:
SELECT TOP 1
id, value
FROM your_table
WHERE id >= 7
ORDER BY id
or for MySql
SELECT id, value
FROM your_table
WHERE id >= 7
ORDER BY id
LIMIT 0,1
I would simply do it like this:
select top 1 * from myTable where id >=7
order by id
implementation of the top 1
part is T-SQL (MSSQL/Sybase), other implementations vary but it is always possible (mysql/postgre LIMIT 1
, oracle rownum = 1
)
select top 1 * from Persons where Id >= @Id order by Id
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