鍍金池/ 教程/ 數(shù)據(jù)庫(kù)/ SQL TOP,LIMIT,ROWNUM子句
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SQL TOP,LIMIT,ROWNUM子句

SQL TOP子句用于從表中獲取一個(gè)TOP N數(shù)字或X%的紀(jì)錄。

注意: 不是所有的數(shù)據(jù)庫(kù)都支持TOP子句。例如,MySQL使用LIMIT子句來(lái)獲取記錄;Oracle使用ROWNUM獲取有限的記錄數(shù)。

語(yǔ)法

SELECT語(yǔ)句TOP子句的基本語(yǔ)法將如下所示:

SELECT TOP number|percent column_name(s)
FROM table_name
WHERE [condition]

例子:

考慮CUSTOMERS表具有以下記錄:

+----+----------+-----+-----------+----------+
| ID | NAME     | AGE | ADDRESS   | SALARY   |
+----+----------+-----+-----------+----------+
|  1 | Ramesh   |  32 | Ahmedabad |  2000.00 |
|  2 | Khilan   |  25 | Delhi     |  1500.00 |
|  3 | kaushik  |  23 | Kota      |  2000.00 |
|  4 | Chaitali |  25 | Mumbai    |  6500.00 |
|  5 | Hardik   |  27 | Bhopal    |  8500.00 |
|  6 | Komal    |  22 | MP        |  4500.00 |
|  7 | Muffy    |  24 | Indore    | 10000.00 |
+----+----------+-----+-----------+----------+

以下是SQL SERVER服務(wù)器,這將取前客戶表的前3個(gè)記錄的例子:

SQL> SELECT TOP 3 * FROM CUSTOMERS;

這將產(chǎn)生以下結(jié)果:

+----+---------+-----+-----------+---------+
| ID | NAME    | AGE | ADDRESS   | SALARY  |
+----+---------+-----+-----------+---------+
|  1 | Ramesh  |  32 | Ahmedabad | 2000.00 |
|  2 | Khilan  |  25 | Delhi     | 1500.00 |
|  3 | kaushik |  23 | Kota      | 2000.00 |
+----+---------+-----+-----------+---------+

如果你使用MySQL服務(wù)器,然后在這里是一個(gè)等效的例子:

SQL> SELECT * FROM CUSTOMERS
LIMIT 3;

這將產(chǎn)生以下結(jié)果:

+----+---------+-----+-----------+---------+
| ID | NAME    | AGE | ADDRESS   | SALARY  |
+----+---------+-----+-----------+---------+
|  1 | Ramesh  |  32 | Ahmedabad | 2000.00 |
|  2 | Khilan  |  25 | Delhi     | 1500.00 |
|  3 | kaushik |  23 | Kota      | 2000.00 |
+----+---------+-----+-----------+---------+

如果您使用Oracle服務(wù)器,然后在這里是一個(gè)等效的例子:

SQL> SELECT * FROM CUSTOMERS
WHERE ROWNUM <= 3;

這將產(chǎn)生以下結(jié)果:

+----+---------+-----+-----------+---------+
| ID | NAME    | AGE | ADDRESS   | SALARY  |
+----+---------+-----+-----------+---------+
|  1 | Ramesh  |  32 | Ahmedabad