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發表時間：2016/1/26 12:48 |
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- 註冊日: 2008/2/19
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- [分享]SQL SELECT TOP Clause
- SQL SELECT TOP Clause
The SELECT TOP clause is used to specify the number of records to return.
The SELECT TOP clause can be very useful on large tables with thousands of records. Returning a large number of records can impact on performance.
Note: Not all database systems support the SELECT TOP clause.
SQL Server / MS Access Syntax
SELECT TOP number|percent column_name(s) FROM table_name;
SQL SELECT TOP Equivalent in MySQL and Oracle
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 following SQL statement selects the two first records from the "Customers" table:
Example
SELECT TOP 2 * FROM Customers;
SQL SELECT TOP PERCENT Example
The following SQL statement selects the first 50% of the records from the "Customers" table:
Example
SELECT TOP 50 PERCENT * FROM Customers;
原文出處：SQL SELECT TOP, LIMIT, ROWNUM
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[分享]SQL SELECT TOP Clause (冷日