How to use several top clauses in a database __ database

use of top statements in different databases

Syntax for SQL Server:

SELECT Top number|percentCOLUMN_NAME (s) from table_name

The SQL SELECT top in MySQL and Oracle is equivalent.

MySQL Syntax:

SELECT column_name (s) from table_name LIMIT Number

Example:

SELECT * from Persons LIMIT 5

Oracle Syntax:

SELECT column_name (s) from table_name WHERE rownum <=Number

Example:

SELECT * from Persons WHERE rownum <= 5

The original table (in the example):

Persons table:

Address City

Id	LastName	FirstName
1	Adams	John	Oxford Street	London
2	Bush	George	Fifth Avenue	New York
3	Carter	Thomas	Changan Street	Beijing
4	Obama	Barack	Pennsylvania Avenue	Washington

SQL Top Instance

Now we want to select the first two records from the "Persons" table above.

We can use the following SELECT statement:

SELECT Top 2 * from Persons

Results:

Address City

Id	LastName	FirstName
1	Adams	John	Oxford Street	London
2	Bush	George	Fifth Avenue	New York

SQL Top PERCENT instance

Now, we want to select 50% of the records from the "Persons" table above.

We can use the following SELECT statement:

SELECT Top PERCENT * from Persons

Results:

Address City

Id	LastName	FirstName
1	Adams	John	Oxford Street	London
2	Bush	George	Fifth Avenue	New York

Add:

Limit can implement top N query, also can implement m to N ( a paragraph) of the record query, the specific syntax is as follows:

LIMIT Offset, Recnum
Where offset is started from the first few (m+1) Records, Recnum is the number of record bars returned. Cases:

Limit 2, 5