Returning TOP N Records

Returning only the first N records in a SQL query differs quite a bit between database platforms. Here's some samples:

Microsoft SQL Server

SELECT TOP 10 column FROM table 

PostgreSQL and MySQL

SELECT column FROM table LIMIT 10 

Oracle

SELECT column FROM table WHERE ROWNUM <= 10 

Sybase

SET rowcount 10 SELECT column FROM table 

Firebird

SELECT FIRST 10 column  FROM table 

Due to these differences if you want to keep your code database independent you should use the maxrows attribute in the cfquery tag in ColdFusion. The tradeoffs to database independance is performance, I would expect maxrows to be slower than specifying the rows in the SQL.

<cfquery datasource="#ds#" maxrows="10"> SELECT column FROM table </cfquery> 

PostgreSQL and MySQL have a cool feature that will let you return an arbitrary range of rows (eg return rows 10-20). This is very handy for displaying pages of records:

SELECT column FROM table LIMIT 10 OFFSET 20 

The above query will return rows 20-30

转载于:https://www.cnblogs.com/binlyzhuo/archive/2010/06/25/1765064.html