SQL - 仅选择前10行？

Question

如何仅选择查询的前10个结果？

我想只显示以下查询的前10个结果:

SELECT a.names,
         COUNT(b.post_title) AS num
    FROM wp_celebnames a
    JOIN wp_posts b ON INSTR(b.post_title, a.names) > 0
    WHERE b.post_date > DATE_SUB(CURDATE(), INTERVAL 1 DAY)
GROUP BY a.names
ORDER BY num DESC

Answer 1

在SQL Server中,使用:

select top 10 ...

例如

select top 100 * from myTable
select top 100 colA, colB from myTable

在MySQL中,使用:

select ... order by num desc limit 10

Answer 2

取决于您的RDBMS

MS SQL Server

SELECT TOP 10 ...

MySQL的

SELECT ... LIMIT 10

SYBASE

SET ROWCOUNT 10
SELECT ...

等等.

Answer 3

在MySQL中:

SELECT * FROM `table` LIMIT 0, 10

Answer 4

神谕

WHERE ROWNUM <= 10  and whatever_else ;

ROWNUM是一个神奇的变量,它包含每一行的序列号1 .. n.

Answer 5

ANSI SQL的答案是FETCH FIRST.

SELECT a.names,
         COUNT(b.post_title) AS num
    FROM wp_celebnames a
    JOIN wp_posts b ON INSTR(b.post_title, a.names) > 0
    WHERE b.post_date > DATE_SUB(CURDATE(), INTERVAL 1 DAY)
GROUP BY a.names
ORDER BY num DESC
FETCH FIRST 10 ROWS ONLY

如果你想要包括关系,请FETCH FIRST 10 ROWS WITH TIES改为.

要跳过指定的行数,请使用OFFSET,例如

...
ORDER BY num DESC
OFFSET 20
FETCH FIRST 10 ROWS ONLY

将跳过前20行,然后获取10行.

由较新版本的Oracle,PostgreSQL,MS SQL Server,Mimer SQL和DB2等提供支持.

Answer 6

DB2

... FETCH FIRST 10 ROWS ONLY