第 7 章 Functions and Operators

count()

SELECT (SELECT count(1) FROM ecs_category) as 'Export category count',
	(SELECT count(1) FROM ecs_goods) as 'Goods count',
	(SELECT count(1) FROM ecs_goods_attr) as 'Attr count';
		</screen>
	</section>
	<section id="group_concat">
		<title>group_concat() 列传行</title>
		<para></para>
		<screen><![CDATA[
SELECT tags FROM neo.article;

linux
redis
mysql
java
php
		

tags字段专为一行显示

SELECT group_concat(tags) FROM neo.article;		

linux,redis,mysql,java,php
		

distinct 去除重复数据

select group_concat(distinct author) from neo.article;		
		

以id分组，把name字段的值打印在一行，分号分隔

select id,group_concat(tags separator ';') from neo.article group by tags;		
		

排序结果

select group_concat(distinct author order by author desc) from neo.article;